CVE-2026-2833

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-2833", "assignerOrgId": "a22f1246-ba21-4bb4-a601-ad51614c1513", "state": "PUBLISHED", "assignerShortName": "cloudflare", "dateReserved": "2026-02-19T21:02:12.382Z", "datePublished": "2026-03-04T23:20:51.985Z", "dateUpdated": "2026-03-06T18:26:03.825Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "product": "https://github.com/cloudflare/pingora", "repo": "https://github.com/cloudflare/pingora", "vendor": "Cloudflare", "versions": [{"lessThan": "0.8.0", "status": "affected", "version": "0", "versionType": "semver"}]}], "credits": [{"lang": "en", "type": "reporter", "value": "Rajat Raghav (xclow3n)"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<span style=\"background-color: transparent;\">An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.<br><br></span><p><span style=\"background-color: transparent;\">Impact</span></p><p><span style=\"background-color: transparent;\">This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:</span></p><ul><li><p><span style=\"background-color: transparent;\">Bypass proxy-level ACL controls and WAF logic</span></p></li></ul><ul><li><p><span style=\"background-color: transparent;\">Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests</span></p></li></ul><ul><li><p><span style=\"background-color: transparent;\">Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP</span></p></li></ul><p><span style=\"background-color: transparent;\">Cloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.</span></p><br><p><span style=\"background-color: transparent;\">Mitigation:</span></p><p><span style=\"background-color: transparent;\">Pingora users should upgrade to Pingora v0.8.0 or higher</span><span style=\"background-color: transparent;\"><br></span></p><b></b><p><span style=\"background-color: transparent;\">As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.</span></p>"}], "value": "An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.\n\nImpact\n\nThis vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:\n\n * Bypass proxy-level ACL controls and WAF logic\n\n\n\n\n * Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests\n\n\n\n\n * Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP\n\n\n\n\nCloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.\n\n\nMitigation:\n\nPingora users should upgrade to Pingora v0.8.0 or higher\n\n\nAs a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse."}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "baseScore": 9.3, "baseSeverity": "CRITICAL", "exploitMaturity": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "HIGH", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-444", "description": "CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "a22f1246-ba21-4bb4-a601-ad51614c1513", "shortName": "cloudflare", "dateUpdated": "2026-03-04T23:20:51.985Z"}, "references": [{"url": "https://github.com/cloudflare/pingora"}], "solutions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "Pingora users should upgrade to Pingora v0.8.0 or higher<br>"}], "value": "Pingora users should upgrade to Pingora v0.8.0 or higher"}], "source": {"discovery": "UNKNOWN"}, "title": "HTTP Request Smuggling via Premature Upgrade", "workarounds": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.<br>"}], "value": "As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse."}], "x_generator": {"engine": "Vulnogram 0.5.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-03-06T18:25:53.691901Z", "id": "CVE-2026-2833", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-03-06T18:26:03.825Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-2833", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-03-06T18:25:53.691901Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-03-06T18:25:58.644Z"}}], "cna": {"title": "HTTP Request Smuggling via Premature Upgrade", "source": {"discovery": "UNKNOWN"}, "credits": [{"lang": "en", "type": "reporter", "value": "Rajat Raghav (xclow3n)"}], "metrics": [{"format": "CVSS", "cvssV4_0": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 9.3, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N", "exploitMaturity": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "userInteraction": "NONE", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "subIntegrityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"repo": "https://github.com/cloudflare/pingora", "vendor": "Cloudflare", "product": "https://github.com/cloudflare/pingora", "versions": [{"status": "affected", "version": "0", "lessThan": "0.8.0", "versionType": "semver"}], "defaultStatus": "unaffected"}], "solutions": [{"lang": "en", "value": "Pingora users should upgrade to Pingora v0.8.0 or higher", "supportingMedia": [{"type": "text/html", "value": "Pingora users should upgrade to Pingora v0.8.0 or higher<br>", "base64": false}]}], "references": [{"url": "https://github.com/cloudflare/pingora"}], "workarounds": [{"lang": "en", "value": "As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.", "supportingMedia": [{"type": "text/html", "value": "As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.<br>", "base64": false}]}], "x_generator": {"engine": "Vulnogram 0.5.0"}, "descriptions": [{"lang": "en", "value": "An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.\n\nImpact\n\nThis vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:\n\n * Bypass proxy-level ACL controls and WAF logic\n\n\n\n\n * Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests\n\n\n\n\n * Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP\n\n\n\n\nCloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.\n\n\nMitigation:\n\nPingora users should upgrade to Pingora v0.8.0 or higher\n\n\nAs a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.", "supportingMedia": [{"type": "text/html", "value": "<span style=\"background-color: transparent;\">An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.<br><br></span><p><span style=\"background-color: transparent;\">Impact</span></p><p><span style=\"background-color: transparent;\">This vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:</span></p><ul><li><p><span style=\"background-color: transparent;\">Bypass proxy-level ACL controls and WAF logic</span></p></li></ul><ul><li><p><span style=\"background-color: transparent;\">Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests</span></p></li></ul><ul><li><p><span style=\"background-color: transparent;\">Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP</span></p></li></ul><p><span style=\"background-color: transparent;\">Cloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.</span></p><br><p><span style=\"background-color: transparent;\">Mitigation:</span></p><p><span style=\"background-color: transparent;\">Pingora users should upgrade to Pingora v0.8.0 or higher</span><span style=\"background-color: transparent;\"><br></span></p><b></b><p><span style=\"background-color: transparent;\">As a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse.</span></p>", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-444", "description": "CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')"}]}], "providerMetadata": {"orgId": "a22f1246-ba21-4bb4-a601-ad51614c1513", "shortName": "cloudflare", "dateUpdated": "2026-03-04T23:20:51.985Z"}}}, "cveMetadata": {"cveId": "CVE-2026-2833", "state": "PUBLISHED", "dateUpdated": "2026-03-06T18:26:03.825Z", "dateReserved": "2026-02-19T21:02:12.382Z", "assignerOrgId": "a22f1246-ba21-4bb4-a601-ad51614c1513", "datePublished": "2026-03-04T23:20:51.985Z", "assignerShortName": "cloudflare"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "https://github.com/cloudflare/pingora", "repo": "https://github.com/cloudflare/pingora", "vendor": "Cloudflare", "versions": [{"lessThan": "0.8.0", "status": "affected", "version": "0", "versionType": "semver"}]}], "source": "cna@cloudflare.com"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:cloudflare:pingora:*:*:*:*:*:*:*:*", "matchCriteriaId": "7FD8B659-5061-46DA-8A73-2E17D6298546", "versionEndExcluding": "0.8.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "An HTTP request smuggling vulnerability (CWE-444) was found in Pingora's handling of HTTP/1.1 connection upgrades. The issue occurs when a Pingora proxy reads a request containing an Upgrade header, causing the proxy to pass through the rest of the bytes on the connection to a backend before the backend has accepted the upgrade. An attacker can thus directly forward a malicious payload after a request with an Upgrade header to that backend in a way that may be interpreted as a subsequent request header, bypassing proxy-level security controls and enabling cross-user session hijacking.\n\nImpact\n\nThis vulnerability primarily affects standalone Pingora deployments where a Pingora proxy is exposed to external traffic. An attacker could exploit this to:\n\n * Bypass proxy-level ACL controls and WAF logic\n\n\n\n\n * Poison caches and upstream connections, causing subsequent requests from legitimate users to receive responses intended for smuggled requests\n\n\n\n\n * Perform cross-user attacks by hijacking sessions or smuggling requests that appear to originate from the trusted proxy IP\n\n\n\n\nCloudflare's CDN infrastructure was not affected by this vulnerability, as ingress proxies in the CDN stack maintain proper HTTP parsing boundaries and do not prematurely switch to upgraded connection forwarding mode.\n\n\nMitigation:\n\nPingora users should upgrade to Pingora v0.8.0 or higher\n\n\nAs a workaround, users may return an error on requests with the Upgrade header present in their request filter logic in order to stop processing bytes beyond the request header and disable downstream connection reuse."}, {"lang": "es", "value": "Se encontr\u00f3 una vulnerabilidad de contrabando de solicitudes HTTP (CWE-444) en el manejo de Pingora de las actualizaciones de conexi\u00f3n HTTP/1.1. El problema ocurre cuando un proxy de Pingora lee una solicitud que contiene un encabezado Upgrade, haciendo que el proxy pase el resto de los bytes de la conexi\u00f3n a un backend antes de que el backend haya aceptado la actualizaci\u00f3n. Un atacante puede as\u00ed reenviar directamente una carga \u00fatil maliciosa despu\u00e9s de una solicitud con un encabezado Upgrade a ese backend de una manera que puede ser interpretada como un encabezado de solicitud subsiguiente, eludiendo los controles de seguridad a nivel de proxy y permitiendo el secuestro de sesi\u00f3n entre usuarios.\n\nImpacto\n\nEsta vulnerabilidad afecta principalmente a implementaciones de Pingora independientes donde un proxy de Pingora est\u00e1 expuesto al tr\u00e1fico externo. Un atacante podr\u00eda explotar esto para:\n\n * Eludir los controles ACL a nivel de proxy y la l\u00f3gica WAF\n\n * Envenenar cach\u00e9s y conexiones ascendentes, haciendo que las solicitudes subsiguientes de usuarios leg\u00edtimos reciban respuestas destinadas a solicitudes de contrabando\n\n * Realizar ataques entre usuarios secuestrando sesiones o contrabandeando solicitudes que parecen originarse de la IP del proxy de confianza\n\nLa infraestructura CDN de Cloudflare no se vio afectada por esta vulnerabilidad, ya que los proxies de entrada en la pila CDN mantienen l\u00edmites de an\u00e1lisis HTTP adecuados y no cambian prematuramente al modo de reenv\u00edo de conexi\u00f3n actualizada.\n\nMitigaci\u00f3n:\n\nLos usuarios de Pingora deber\u00edan actualizar a Pingora v0.8.0 o superior\n\nComo soluci\u00f3n alternativa, los usuarios pueden devolver un error en solicitudes con el encabezado Upgrade presente en su l\u00f3gica de filtro de solicitudes para detener el procesamiento de bytes m\u00e1s all\u00e1 del encabezado de la solicitud y deshabilitar la reutilizaci\u00f3n de la conexi\u00f3n descendente."}], "id": "CVE-2026-2833", "lastModified": "2026-06-17T10:31:51.227", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 9.1, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.2, "source": "nvd@nist.gov", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 9.3, "baseSeverity": "CRITICAL", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "HIGH", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "cna@cloudflare.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-2833", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-03-06T18:25:53.691901Z", "version": "2.0.3"}}]}, "published": "2026-03-05T00:15:57.650", "references": [{"source": "cna@cloudflare.com", "tags": ["Product"], "url": "https://github.com/cloudflare/pingora"}], "sourceIdentifier": "cna@cloudflare.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-444"}], "source": "cna@cloudflare.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,0.8.0)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "manual", "scores": [{"score": 100.0, "source": "manual"}]}, "original": {"product": "https://github.com/cloudflare/pingora", "source": "cna", "vendor": "Cloudflare"}, "product": "pingora", "vendor": "cloudflare"}], "analysis": {"en": {"generated_at": "2026-04-17T13:00:45.833937+00:00", "value": {"mitigation_remediation": ["Upgrade Pingora to version 0.8.0 or later to apply the vendor patch", "If an upgrade is not immediately possible, block upstream requests that contain an Upgrade header by configuring the filter logic to return an error response and terminate further processing, thereby preventing downstream connection reuse", "Deploy network\u2011level monitoring to detect anomalous Upgrade header traffic and apply temporary rate limits or IP blocking for sources that exhibit suspicious patterns"], "summary": {"action": "Immediate Patch", "impact": "Cross\u2011user session hijacking and ACL bypass"}, "threat_synthesis": {"affected_systems": "The vulnerability impacts standalone deployments of Cloudflare Pingora that are exposed directly to external traffic. Users running versions prior to v0.8.0 are affected; all newer releases incorporate the fix. The problem does not affect Cloudflare\u2019s CDN ingress proxies, which enforce proper HTTP parsing boundaries.", "description_and_impact": "An HTTP request smuggling flaw in Pingora\u2019s handling of HTTP/1.1 connection upgrades allows an attacker to send a request that contains an Upgrade header. The proxy forwards the rest of the received bytes to the backend before the backend has processed the upgrade request, causing the following bytes to be interpreted as a separate HTTP request. This can bypass proxy\u2011level ACLs, WAF rules, and other security controls, leading to session hijacking, cache poisoning, and cross\u2011user attacks. The weakness is identified as CWE\u2011444 and is defined as a high\u2011severity request smuggling vulnerability.", "risk_and_exploitability": "The CVSS score of 9.3 signals a critical risk, but the EPSS score of less than 1% indicates that exploitation is currently considered unlikely by industry metrics. The flaw is not listed in CISA\u2019s KEV catalog, suggesting no known active exploitation yet. Because the attack requires crafting a specially formatted HTTP request that includes an Upgrade header, the vector is network\u2011based; any host reachable over HTTP/1.1 can serve as a target. If an attacker succeeds, the immediate consequence is ability to issue arbitrary requests to backends from the perspective of the trusted proxy, enabling policy bypass and session hijacking."}}}}, "created": "2026-03-05T09:05:33.040589+00:00", "updated": "2026-04-17T13:15:19.646578+00:00", "vendors": ["cloudflare", "cloudflare$PRODUCT$pingora"]}