CVE-2026-1721

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-1721", "assignerOrgId": "a22f1246-ba21-4bb4-a601-ad51614c1513", "state": "PUBLISHED", "assignerShortName": "cloudflare", "dateReserved": "2026-01-30T20:12:22.668Z", "datePublished": "2026-02-13T01:46:48.674Z", "dateUpdated": "2026-02-27T14:51:31.817Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://github.com/cloudflare", "defaultStatus": "unaffected", "packageName": "agents", "repo": "https://github.com/cloudflare/agents", "versions": [{"lessThan": "0.3.10", "status": "affected", "version": "0", "versionType": "git"}]}], "credits": [{"lang": "en", "type": "reporter", "value": "Nishant Kumawat"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p><span style=\"background-color: transparent;\"><b>Summary</b></span></p><p><span style=\"background-color: transparent;\">A Reflected Cross-Site Scripting (XSS) vulnerability was discovered in the AI Playground's OAuth callback handler. The `error_description` query parameter was directly interpolated into an HTML script tag without proper escaping, allowing attackers to execute arbitrary JavaScript in the context of the victim's session.</span></p><p><span style=\"background-color: transparent;\"><br></span></p><p><span style=\"background-color: transparent;\"><b>Root cause</b></span></p><p><span style=\"background-color: transparent;\">The OAuth callback handler in `site/ai-playground/src/server.ts` directly interpolated the `authError` value, sourced from the `error_description` query parameter, into an inline `&lt;script&gt;` tag.</span></p><b><br></b><p><span style=\"background-color: transparent;\"><b>Impact</b></span></p><p><span style=\"background-color: transparent;\">An attacker could craft a malicious link that, when clicked by a victim, would:</span></p><ol><li><p><span style=\"background-color: transparent;\">Steal user chat message history - Access all LLM interactions stored in the user's session.</span></p></li><li><p><span style=\"background-color: transparent;\">Access connected MCP Servers - Interact with any MCP servers connected to the victim's session (public or authenticated/private), potentially allowing the attacker to perform actions on the victim's behalf</span></p></li></ol><div><b><p><span style=\"background-color: transparent;\"><br></span></p><p><span style=\"background-color: transparent;\">Mitigation:</span></p></b><ul><li><p><span style=\"background-color: transparent;\">PR:&nbsp;</span><a target=\"_blank\" rel=\"nofollow\" href=\"https://github.com/cloudflare/agents/pull/841\"><span style=\"background-color: transparent;\">https://github.com/cloudflare/agents/pull/841</span></a></p></li></ul><ul><li><p><span style=\"background-color: transparent;\">Agents-sdk users should upgrade to&nbsp;</span><span style=\"background-color: transparent;\">agents@0.3.10</span></p></li></ul><ul><li><p><span style=\"background-color: transparent;\">Developers using configureOAuthCallback with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.</span></p></li></ul></div><br>"}], "value": "Summary\n\nA Reflected Cross-Site Scripting (XSS) vulnerability was discovered in the AI Playground's OAuth callback handler. The `error_description` query parameter was directly interpolated into an HTML script tag without proper escaping, allowing attackers to execute arbitrary JavaScript in the context of the victim's session.\n\n\n\n\nRoot cause\n\nThe OAuth callback handler in `site/ai-playground/src/server.ts` directly interpolated the `authError` value, sourced from the `error_description` query parameter, into an inline `<script>` tag.\n\n\nImpact\n\nAn attacker could craft a malicious link that, when clicked by a victim, would:\n\n * Steal user chat message history - Access all LLM interactions stored in the user's session.\n\n\n * Access connected MCP Servers - Interact with any MCP servers connected to the victim's session (public or authenticated/private), potentially allowing the attacker to perform actions on the victim's behalf\n\n\n\n\n\nMitigation:\n\n * PR:\u00a0 https://github.com/cloudflare/agents/pull/841 https://github.com/cloudflare/agents/pull/841 \n\n\n\n\n * Agents-sdk users should upgrade to\u00a0agents@0.3.10\n\n\n\n\n * Developers using configureOAuthCallback with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation."}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "baseScore": 6.2, "baseSeverity": "MEDIUM", "exploitMaturity": "NOT_DEFINED", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "LOW", "userInteraction": "ACTIVE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "providerMetadata": {"orgId": "a22f1246-ba21-4bb4-a601-ad51614c1513", "shortName": "cloudflare", "dateUpdated": "2026-02-13T01:48:24.571Z"}, "references": [{"url": "https://github.com/cloudflare/agents/pull/841"}], "solutions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<ul><li><p><span style=\"background-color: transparent;\">PR: </span><a target=\"_blank\" rel=\"nofollow\" href=\"https://github.com/cloudflare/agents/pull/841\"><span style=\"background-color: transparent;\">https://github.com/cloudflare/agents/pull/841</span></a></p></li></ul><ul><li><p><span style=\"background-color: transparent;\">Agents-sdk users should upgrade to `</span><code><span style=\"background-color: transparent;\">agents@0.3.10`</span></code></p></li><li><p><span style=\"background-color: transparent;\">Developers using `</span>configureOAuthCallback`<span style=\"background-color: transparent;\"> with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.</span></p></li></ul>"}], "value": "* PR: https://github.com/cloudflare/agents/pull/841 https://github.com/cloudflare/agents/pull/841 \n\n\n\n\n * Agents-sdk users should upgrade to `agents@0.3.10`\n\n\n * Developers using `configureOAuthCallback` with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation."}], "source": {"discovery": "UNKNOWN"}, "title": "Reflected Cross-Site Scripting (XSS) vulnerability in AI Playground site", "x_generator": {"engine": "Vulnogram 0.5.0"}}, "adp": [{"problemTypes": [{"descriptions": [{"type": "CWE", "cweId": "CWE-79", "lang": "en", "description": "CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')"}]}], "metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-02-13T13:10:24.218273Z", "id": "CVE-2026-1721", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"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": "2026-02-27T14:51:31.817Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-1721", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-02-13T13:10:24.218273Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-79", "description": "CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')"}]}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-02-13T13:10:31.049Z"}}], "cna": {"title": "Reflected Cross-Site Scripting (XSS) vulnerability in AI Playground site", "source": {"discovery": "UNKNOWN"}, "credits": [{"lang": "en", "type": "reporter", "value": "Nishant Kumawat"}], "metrics": [{"format": "CVSS", "cvssV4_0": {"Safety": "NOT_DEFINED", "version": "4.0", "Recovery": "NOT_DEFINED", "baseScore": 6.2, "Automatable": "NOT_DEFINED", "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N", "exploitMaturity": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "userInteraction": "ACTIVE", "attackComplexity": "LOW", "attackRequirements": "NONE", "privilegesRequired": "NONE", "subIntegrityImpact": "LOW", "vulnIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"repo": "https://github.com/cloudflare/agents", "versions": [{"status": "affected", "version": "0", "lessThan": "0.3.10", "versionType": "git"}], "packageName": "agents", "collectionURL": "https://github.com/cloudflare", "defaultStatus": "unaffected"}], "solutions": [{"lang": "en", "value": "* PR: https://github.com/cloudflare/agents/pull/841 https://github.com/cloudflare/agents/pull/841 \n\n\n\n\n * Agents-sdk users should upgrade to `agents@0.3.10`\n\n\n * Developers using `configureOAuthCallback` with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.", "supportingMedia": [{"type": "text/html", "value": "<ul><li><p><span style=\"background-color: transparent;\">PR: </span><a target=\"_blank\" rel=\"nofollow\" href=\"https://github.com/cloudflare/agents/pull/841\"><span style=\"background-color: transparent;\">https://github.com/cloudflare/agents/pull/841</span></a></p></li></ul><ul><li><p><span style=\"background-color: transparent;\">Agents-sdk users should upgrade to `</span><code><span style=\"background-color: transparent;\">agents@0.3.10`</span></code></p></li><li><p><span style=\"background-color: transparent;\">Developers using `</span>configureOAuthCallback`<span style=\"background-color: transparent;\"> with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.</span></p></li></ul>", "base64": false}]}], "references": [{"url": "https://github.com/cloudflare/agents/pull/841"}], "x_generator": {"engine": "Vulnogram 0.5.0"}, "descriptions": [{"lang": "en", "value": "Summary\n\nA Reflected Cross-Site Scripting (XSS) vulnerability was discovered in the AI Playground's OAuth callback handler. The `error_description` query parameter was directly interpolated into an HTML script tag without proper escaping, allowing attackers to execute arbitrary JavaScript in the context of the victim's session.\n\n\n\n\nRoot cause\n\nThe OAuth callback handler in `site/ai-playground/src/server.ts` directly interpolated the `authError` value, sourced from the `error_description` query parameter, into an inline `<script>` tag.\n\n\nImpact\n\nAn attacker could craft a malicious link that, when clicked by a victim, would:\n\n * Steal user chat message history - Access all LLM interactions stored in the user's session.\n\n\n * Access connected MCP Servers - Interact with any MCP servers connected to the victim's session (public or authenticated/private), potentially allowing the attacker to perform actions on the victim's behalf\n\n\n\n\n\nMitigation:\n\n * PR:\u00a0 https://github.com/cloudflare/agents/pull/841 https://github.com/cloudflare/agents/pull/841 \n\n\n\n\n * Agents-sdk users should upgrade to\u00a0agents@0.3.10\n\n\n\n\n * Developers using configureOAuthCallback with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.", "supportingMedia": [{"type": "text/html", "value": "<p><span style=\"background-color: transparent;\"><b>Summary</b></span></p><p><span style=\"background-color: transparent;\">A Reflected Cross-Site Scripting (XSS) vulnerability was discovered in the AI Playground's OAuth callback handler. The `error_description` query parameter was directly interpolated into an HTML script tag without proper escaping, allowing attackers to execute arbitrary JavaScript in the context of the victim's session.</span></p><p><span style=\"background-color: transparent;\"><br></span></p><p><span style=\"background-color: transparent;\"><b>Root cause</b></span></p><p><span style=\"background-color: transparent;\">The OAuth callback handler in `site/ai-playground/src/server.ts` directly interpolated the `authError` value, sourced from the `error_description` query parameter, into an inline `&lt;script&gt;` tag.</span></p><b><br></b><p><span style=\"background-color: transparent;\"><b>Impact</b></span></p><p><span style=\"background-color: transparent;\">An attacker could craft a malicious link that, when clicked by a victim, would:</span></p><ol><li><p><span style=\"background-color: transparent;\">Steal user chat message history - Access all LLM interactions stored in the user's session.</span></p></li><li><p><span style=\"background-color: transparent;\">Access connected MCP Servers - Interact with any MCP servers connected to the victim's session (public or authenticated/private), potentially allowing the attacker to perform actions on the victim's behalf</span></p></li></ol><div><b><p><span style=\"background-color: transparent;\"><br></span></p><p><span style=\"background-color: transparent;\">Mitigation:</span></p></b><ul><li><p><span style=\"background-color: transparent;\">PR:&nbsp;</span><a target=\"_blank\" rel=\"nofollow\" href=\"https://github.com/cloudflare/agents/pull/841\"><span style=\"background-color: transparent;\">https://github.com/cloudflare/agents/pull/841</span></a></p></li></ul><ul><li><p><span style=\"background-color: transparent;\">Agents-sdk users should upgrade to&nbsp;</span><span style=\"background-color: transparent;\">agents@0.3.10</span></p></li></ul><ul><li><p><span style=\"background-color: transparent;\">Developers using configureOAuthCallback with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation.</span></p></li></ul></div><br>", "base64": false}]}], "providerMetadata": {"orgId": "a22f1246-ba21-4bb4-a601-ad51614c1513", "shortName": "cloudflare", "dateUpdated": "2026-02-13T01:48:24.571Z"}}}, "cveMetadata": {"cveId": "CVE-2026-1721", "state": "PUBLISHED", "dateUpdated": "2026-02-27T14:51:31.817Z", "dateReserved": "2026-01-30T20:12:22.668Z", "assignerOrgId": "a22f1246-ba21-4bb4-a601-ad51614c1513", "datePublished": "2026-02-13T01:46:48.674Z", "assignerShortName": "cloudflare"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"collectionURL": "https://github.com/cloudflare", "defaultStatus": "unaffected", "packageName": "agents", "repo": "https://github.com/cloudflare/agents", "versions": [{"lessThan": "0.3.10", "status": "affected", "version": "0", "versionType": "git"}]}], "source": "cna@cloudflare.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Summary\n\nA Reflected Cross-Site Scripting (XSS) vulnerability was discovered in the AI Playground's OAuth callback handler. The `error_description` query parameter was directly interpolated into an HTML script tag without proper escaping, allowing attackers to execute arbitrary JavaScript in the context of the victim's session.\n\n\n\n\nRoot cause\n\nThe OAuth callback handler in `site/ai-playground/src/server.ts` directly interpolated the `authError` value, sourced from the `error_description` query parameter, into an inline `<script>` tag.\n\n\nImpact\n\nAn attacker could craft a malicious link that, when clicked by a victim, would:\n\n * Steal user chat message history - Access all LLM interactions stored in the user's session.\n\n\n * Access connected MCP Servers - Interact with any MCP servers connected to the victim's session (public or authenticated/private), potentially allowing the attacker to perform actions on the victim's behalf\n\n\n\n\n\nMitigation:\n\n * PR:\u00a0 https://github.com/cloudflare/agents/pull/841 https://github.com/cloudflare/agents/pull/841 \n\n\n\n\n * Agents-sdk users should upgrade to\u00a0agents@0.3.10\n\n\n\n\n * Developers using configureOAuthCallback with custom error handling in their own applications should ensure all user-controlled input is escaped before interpolation."}, {"lang": "es", "value": "Resumen\n\nUna vulnerabilidad de Cross-Site Scripting Reflejado (XSS) fue descubierta en el manejador de callback de OAuth del AI Playground. El par\u00e1metro de consulta `error_description` fue directamente interpolado en una etiqueta de script HTML sin el escape adecuado, permitiendo a los atacantes ejecutar JavaScript arbitrario en el contexto de la sesi\u00f3n de la v\u00edctima.\n\nCausa ra\u00edz\n\nEl manejador de callback de OAuth en `site/ai-playground/src/server.ts` interpol\u00f3 directamente el valor `authError`, obtenido del par\u00e1metro de consulta `error_description`, en una etiqueta `"}], "id": "CVE-2026-1721", "lastModified": "2026-06-17T10:16:23.767", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 6.2, "baseSeverity": "MEDIUM", "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": "LOW", "userInteraction": "ACTIVE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:L/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": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "cna@cloudflare.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-1721", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-02-13T13:10:24.218273Z", "version": "2.0.3"}}]}, "published": "2026-02-13T03:15:52.467", "references": [{"source": "cna@cloudflare.com", "url": "https://github.com/cloudflare/agents/pull/841"}], "sourceIdentifier": "cna@cloudflare.com", "vulnStatus": "Deferred", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-79"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0.0.0,0.3.10)"}}], "product": "agents_sdk", "vendor": "cloudflare"}], "analysis": {"en": {"generated_at": "2026-04-17T19:55:06.556423+00:00", "value": {"mitigation_remediation": ["Upgrade the Cloudflare Agents SDK to version 0.3.10 or newer to apply the official patch that removes the unsafe interpolation.", "If you cannot immediately upgrade, modify your OAuth callback handling to escape all user\u2011controlled input before inserting it into HTML, especially the error_description parameter, thereby preventing script injection.", "For applications that use configureOAuthCallback with custom error handling, ensure that any data derived from query parameters is properly encoded or sanitized before use in the user interface."], "summary": {"action": "Patch", "impact": "Reflected Cross\u2011Site Scripting enabling arbitrary JavaScript execution in a victim\u2019s session"}, "threat_synthesis": {"affected_systems": "Cloudflare AI Playground components that rely on the Cloudflare Agents SDK prior to version 0.3.10. Users who have integrated the SDK and use the configureOAuthCallback function with custom error handling are affected. Upgrading the Agents SDK to 0.3.10 or later removes the vulnerable code path and fixes the interpolation issue.", "description_and_impact": "A reflected XSS flaw exists in the AI Playground OAuth callback handler where the error_description query parameter is directly interpolated into an inline <script> tag without any escaping. This allows an attacker to craft a malicious URL that, when opened by a target user, executes arbitrary JavaScript in the context of that user's session. Such code can read session data, harvest user chat history, and interact with any MCP servers the victim\u2019s session is connected to, potentially executing actions on the victim\u2019s behalf. The weakness is a classic CWE\u201179 injection flaw.", "risk_and_exploitability": "The CVSS score is 6.2, indicating a medium severity. EPSS is below 1%, suggesting a low yet non\u2011zero likelihood of exploitation; the vulnerability is not listed in CISA\u2019s Known Exploited Vulnerabilities catalog. The attack vector requires a victim to click a specially crafted link, so it is a typical phishing or social engineering scenario. Once executed, the attacker can execute JavaScript in the victim\u2019s browser, compromising confidentiality, integrity, and availability of the session data. The overall risk remains moderate due to the lack of widespread exploitation and the need for user interaction."}}}}, "created": "2026-02-13T21:28:51.479993+00:00", "updated": "2026-04-17T20:00:09.028887+00:00", "vendors": ["cloudflare", "cloudflare$PRODUCT$agents_sdk"]}