CVE-2026-28386

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-28386", "assignerOrgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5", "state": "PUBLISHED", "assignerShortName": "openssl", "dateReserved": "2026-02-27T13:45:02.161Z", "datePublished": "2026-04-07T22:00:50.164Z", "dateUpdated": "2026-04-10T20:16:08.389Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "product": "OpenSSL", "vendor": "OpenSSL", "versions": [{"lessThan": "3.6.2", "status": "affected", "version": "3.6.0", "versionType": "semver"}]}], "credits": [{"lang": "en", "type": "reporter", "value": "Stanislav Fort (Aisle Research)"}, {"lang": "en", "type": "reporter", "value": "Pavel Kohout (Aisle Research)"}, {"lang": "en", "type": "reporter", "value": "Alex Gaynor (Anthropic)"}, {"lang": "en", "type": "remediation developer", "value": "Stanislav Fort (Aisle Research)"}, {"lang": "en", "type": "remediation developer", "value": "Pavel Kohout (Aisle Research)"}, {"lang": "en", "type": "remediation developer", "value": "Alex Gaynor (Anthropic)"}], "datePublic": "2026-04-07T14:00:00.000Z", "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "Issue summary: Applications using AES-CFB128 encryption or decryption on<br>systems with AVX-512 and VAES support can trigger an out-of-bounds read<br>of up to 15 bytes when processing partial cipher blocks.<br><br>Impact summary: This out-of-bounds read may trigger a crash which leads to<br>Denial of Service for an application if the input buffer ends at a memory<br>page boundary and the following page is unmapped. There is no information<br>disclosure as the over-read bytes are not written to output.<br><br>The vulnerable code path is only reached when processing partial blocks<br>(when a previous call left an incomplete block and the current call provides<br>fewer bytes than needed to complete it). Additionally, the input buffer<br>must be positioned at a page boundary with the following page unmapped.<br>CFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or<br>ChaCha20-Poly1305 instead. For these reasons the issue was assessed as<br>Low severity according to our Security Policy.<br><br>Only x86-64 systems with AVX-512 and VAES instruction support are affected.<br>Other architectures and systems without VAES support use different code<br>paths that are not affected.<br><br>OpenSSL FIPS module in 3.6 version is affected by this issue."}], "value": "Issue summary: Applications using AES-CFB128 encryption or decryption on\nsystems with AVX-512 and VAES support can trigger an out-of-bounds read\nof up to 15 bytes when processing partial cipher blocks.\n\nImpact summary: This out-of-bounds read may trigger a crash which leads to\nDenial of Service for an application if the input buffer ends at a memory\npage boundary and the following page is unmapped. There is no information\ndisclosure as the over-read bytes are not written to output.\n\nThe vulnerable code path is only reached when processing partial blocks\n(when a previous call left an incomplete block and the current call provides\nfewer bytes than needed to complete it). Additionally, the input buffer\nmust be positioned at a page boundary with the following page unmapped.\nCFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or\nChaCha20-Poly1305 instead. For these reasons the issue was assessed as\nLow severity according to our Security Policy.\n\nOnly x86-64 systems with AVX-512 and VAES instruction support are affected.\nOther architectures and systems without VAES support use different code\npaths that are not affected.\n\nOpenSSL FIPS module in 3.6 version is affected by this issue."}], "metrics": [{"format": "other", "other": {"content": {"text": "Low"}, "type": "https://openssl-library.org/policies/general/security-policy/"}}], "problemTypes": [{"descriptions": [{"cweId": "CWE-125", "description": "CWE-125 Out-of-bounds Read", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5", "shortName": "openssl", "dateUpdated": "2026-04-07T22:00:50.164Z"}, "references": [{"name": "OpenSSL Advisory", "tags": ["vendor-advisory"], "url": "https://openssl-library.org/news/secadv/20260407.txt"}, {"name": "3.6.2 git commit", "tags": ["patch"], "url": "https://github.com/openssl/openssl/commit/61f428a2fc6671ede184a19f71e6e495f0689621"}], "source": {"discovery": "UNKNOWN"}, "title": "Out-of-bounds Read in AES-CFB-128 on X86-64 with AVX-512 Support", "x_generator": {"engine": "Vulnogram 0.2.0"}}, "adp": [{"metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 9.1, "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}}, {"other": {"type": "ssvc", "content": {"timestamp": "2026-04-10T20:15:21.235876Z", "id": "CVE-2026-28386", "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": "2026-04-10T20:16:08.389Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 9.1, "attackVector": "NETWORK", "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "HIGH"}}, {"other": {"type": "ssvc", "content": {"id": "CVE-2026-28386", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-04-10T20:15:21.235876Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-04-10T20:16:01.884Z"}}], "cna": {"title": "Out-of-bounds Read in AES-CFB-128 on X86-64 with AVX-512 Support", "source": {"discovery": "UNKNOWN"}, "credits": [{"lang": "en", "type": "reporter", "value": "Stanislav Fort (Aisle Research)"}, {"lang": "en", "type": "reporter", "value": "Pavel Kohout (Aisle Research)"}, {"lang": "en", "type": "reporter", "value": "Alex Gaynor (Anthropic)"}, {"lang": "en", "type": "remediation developer", "value": "Stanislav Fort (Aisle Research)"}, {"lang": "en", "type": "remediation developer", "value": "Pavel Kohout (Aisle Research)"}, {"lang": "en", "type": "remediation developer", "value": "Alex Gaynor (Anthropic)"}], "metrics": [{"other": {"type": "https://openssl-library.org/policies/general/security-policy/", "content": {"text": "Low"}}, "format": "other"}], "affected": [{"vendor": "OpenSSL", "product": "OpenSSL", "versions": [{"status": "affected", "version": "3.6.0", "lessThan": "3.6.2", "versionType": "semver"}], "defaultStatus": "unaffected"}], "datePublic": "2026-04-07T14:00:00.000Z", "references": [{"url": "https://openssl-library.org/news/secadv/20260407.txt", "name": "OpenSSL Advisory", "tags": ["vendor-advisory"]}, {"url": "https://github.com/openssl/openssl/commit/61f428a2fc6671ede184a19f71e6e495f0689621", "name": "3.6.2 git commit", "tags": ["patch"]}], "x_generator": {"engine": "Vulnogram 0.2.0"}, "descriptions": [{"lang": "en", "value": "Issue summary: Applications using AES-CFB128 encryption or decryption on\nsystems with AVX-512 and VAES support can trigger an out-of-bounds read\nof up to 15 bytes when processing partial cipher blocks.\n\nImpact summary: This out-of-bounds read may trigger a crash which leads to\nDenial of Service for an application if the input buffer ends at a memory\npage boundary and the following page is unmapped. There is no information\ndisclosure as the over-read bytes are not written to output.\n\nThe vulnerable code path is only reached when processing partial blocks\n(when a previous call left an incomplete block and the current call provides\nfewer bytes than needed to complete it). Additionally, the input buffer\nmust be positioned at a page boundary with the following page unmapped.\nCFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or\nChaCha20-Poly1305 instead. For these reasons the issue was assessed as\nLow severity according to our Security Policy.\n\nOnly x86-64 systems with AVX-512 and VAES instruction support are affected.\nOther architectures and systems without VAES support use different code\npaths that are not affected.\n\nOpenSSL FIPS module in 3.6 version is affected by this issue.", "supportingMedia": [{"type": "text/html", "value": "Issue summary: Applications using AES-CFB128 encryption or decryption on<br>systems with AVX-512 and VAES support can trigger an out-of-bounds read<br>of up to 15 bytes when processing partial cipher blocks.<br><br>Impact summary: This out-of-bounds read may trigger a crash which leads to<br>Denial of Service for an application if the input buffer ends at a memory<br>page boundary and the following page is unmapped. There is no information<br>disclosure as the over-read bytes are not written to output.<br><br>The vulnerable code path is only reached when processing partial blocks<br>(when a previous call left an incomplete block and the current call provides<br>fewer bytes than needed to complete it). Additionally, the input buffer<br>must be positioned at a page boundary with the following page unmapped.<br>CFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or<br>ChaCha20-Poly1305 instead. For these reasons the issue was assessed as<br>Low severity according to our Security Policy.<br><br>Only x86-64 systems with AVX-512 and VAES instruction support are affected.<br>Other architectures and systems without VAES support use different code<br>paths that are not affected.<br><br>OpenSSL FIPS module in 3.6 version is affected by this issue.", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-125", "description": "CWE-125 Out-of-bounds Read"}]}], "providerMetadata": {"orgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5", "shortName": "openssl", "dateUpdated": "2026-04-07T22:00:50.164Z"}}}, "cveMetadata": {"cveId": "CVE-2026-28386", "state": "PUBLISHED", "dateUpdated": "2026-04-10T20:16:08.389Z", "dateReserved": "2026-02-27T13:45:02.161Z", "assignerOrgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5", "datePublished": "2026-04-07T22:00:50.164Z", "assignerShortName": "openssl"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "OpenSSL", "vendor": "OpenSSL", "versions": [{"lessThan": "3.6.2", "status": "affected", "version": "3.6.0", "versionType": "semver"}]}], "source": "openssl-security@openssl.org"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*", "matchCriteriaId": "4A9E621D-29D8-418A-BF37-BED333C14507", "versionEndExcluding": "3.6.2", "versionStartIncluding": "3.6.0", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Issue summary: Applications using AES-CFB128 encryption or decryption on\nsystems with AVX-512 and VAES support can trigger an out-of-bounds read\nof up to 15 bytes when processing partial cipher blocks.\n\nImpact summary: This out-of-bounds read may trigger a crash which leads to\nDenial of Service for an application if the input buffer ends at a memory\npage boundary and the following page is unmapped. There is no information\ndisclosure as the over-read bytes are not written to output.\n\nThe vulnerable code path is only reached when processing partial blocks\n(when a previous call left an incomplete block and the current call provides\nfewer bytes than needed to complete it). Additionally, the input buffer\nmust be positioned at a page boundary with the following page unmapped.\nCFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or\nChaCha20-Poly1305 instead. For these reasons the issue was assessed as\nLow severity according to our Security Policy.\n\nOnly x86-64 systems with AVX-512 and VAES instruction support are affected.\nOther architectures and systems without VAES support use different code\npaths that are not affected.\n\nOpenSSL FIPS module in 3.6 version is affected by this issue."}, {"lang": "es", "value": "Resumen del problema: Las aplicaciones que usan cifrado o descifrado AES-CFB128 en sistemas con soporte para AVX-512 y VAES pueden desencadenar una lectura fuera de l\u00edmites de hasta 15 bytes al procesar bloques de cifrado parciales.\n\nResumen del impacto: Esta lectura fuera de l\u00edmites puede desencadenar un fallo que lleva a la denegaci\u00f3n de servicio para una aplicaci\u00f3n si el b\u00fafer de entrada termina en un l\u00edmite de p\u00e1gina de memoria y la p\u00e1gina siguiente no est\u00e1 mapeada. No hay divulgaci\u00f3n de informaci\u00f3n ya que los bytes le\u00eddos en exceso no se escriben en la salida.\n\nLa ruta de c\u00f3digo vulnerable solo se alcanza al procesar bloques parciales (cuando una llamada anterior dej\u00f3 un bloque incompleto y la llamada actual proporciona menos bytes de los necesarios para completarlo). Adem\u00e1s, el b\u00fafer de entrada debe estar posicionado en un l\u00edmite de p\u00e1gina con la p\u00e1gina siguiente sin mapear. El modo CFB no se usa en los protocolos TLS/DTLS, que usan CBC, GCM, CCM o ChaCha20-Poly1305 en su lugar. Por estas razones, el problema fue evaluado como de severidad Baja seg\u00fan nuestra Pol\u00edtica de Seguridad.\n\nSolo los sistemas x86-64 con soporte para instrucciones AVX-512 y VAES est\u00e1n afectados. Otras arquitecturas y sistemas sin soporte VAES usan rutas de c\u00f3digo diferentes que no est\u00e1n afectadas.\n\nEl m\u00f3dulo OpenSSL FIPS en la versi\u00f3n 3.6 est\u00e1 afectado por este problema."}], "id": "CVE-2026-28386", "lastModified": "2026-07-24T23:10:00.563", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.1, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.2, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-28386", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-04-10T20:15:21.235876Z", "version": "2.0.3"}}]}, "published": "2026-04-07T22:16:20.513", "references": [{"source": "openssl-security@openssl.org", "tags": ["Patch"], "url": "https://github.com/openssl/openssl/commit/61f428a2fc6671ede184a19f71e6e495f0689621"}, {"source": "openssl-security@openssl.org", "tags": ["Vendor Advisory"], "url": "https://openssl-library.org/news/secadv/20260407.txt"}], "sourceIdentifier": "openssl-security@openssl.org", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-125"}], "source": "openssl-security@openssl.org", "type": "Secondary"}]}

{"bugzilla": {"description": "openssl: openssl: Denial of Service due to out-of-bounds read in AES-CFB128", "id": "2451099", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2451099"}, "csaw": false, "cvss3": {"cvss3_base_score": "4.7", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-805", "details": ["A flaw was found in openssl. Applications using AES-CFB128 encryption or decryption on systems with AVX-512 and VAES support may experience a Denial of Service (DoS). This occurs when processing partial cipher blocks, specifically if the input buffer ends at a memory page boundary and the subsequent page is unmapped. This can lead to an out-of-bounds read of up to 15 bytes and a potential application crash."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}, "name": "CVE-2026-28386", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "edk2", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "openssl", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "shim", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "shim-unsigned-aarch64", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "shim-unsigned-x64", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Fix deferred", "package_name": "openssl", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Fix deferred", "package_name": "openssl", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Fix deferred", "package_name": "ovmf", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "compat-openssl10", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "edk2", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "mingw-openssl", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "openssl", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "shim", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Fix deferred", "package_name": "shim-unsigned-x64", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "compat-openssl11", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "edk2", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "openssl", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "shim", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "shim-unsigned-aarch64", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "package_name": "shim-unsigned-x64", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Not affected", "package_name": "openssl", "product_name": "Red Hat Hardened Images"}, {"cpe": "cpe:/a:redhat:jboss_core_services:1", "fix_state": "Fix deferred", "package_name": "openssl", "product_name": "Red Hat JBoss Core Services"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Fix deferred", "package_name": "rhcos", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-04-07T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-28386\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-28386\nhttps://openssl-library.org/news/secadv/20260407.txt"], "statement": "This vulnerability has a Low impact on Red Hat products. It affects applications utilizing AES-CFB128 encryption or decryption on systems equipped with AVX-512 and VAES, potentially leading to a Denial of Service due to an out-of-bounds read when processing partial cipher blocks under specific memory conditions. The CFB mode is not employed in widely used protocols such as TLS/DTLS, which limits the applicability of this flaw.", "threat_severity": "Low"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.6.0,3.6.2)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "OpenSSL", "source": "cna", "vendor": "OpenSSL"}, "product": "openssl", "vendor": "openssl"}], "analysis": {"en": {"generated_at": "2026-04-10T22:40:25.610132+00:00", "value": {"mitigation_remediation": ["Upgrade OpenSSL to the latest patch that removes the AVX\u2011512 accelerated AES\u2011CFB128 path, including the FIPS module; the corrective commit is referenced in the official advisory.\nIf a patch is not yet available, avoid using AES\u2011CFB128 with AVX\u2011512 on x86\u201164 or binary\u2011compile OpenSSL with \"-mno-avx512\" to disable the vulnerable code path.\nEnsure any deployed binaries are built with the latest OpenSSL release and confirm that no ciphertext is processed on page boundaries with unmapped adjacent pages.\nRegularly review vendor advisories and update OpenSSL patches as they become available."], "summary": {"action": "Apply Patch", "impact": "Denial of Service"}, "threat_synthesis": {"affected_systems": "Affects OpenSSL versions that use the AVX\u2011512 accelerated AES\u2011CFB128 path on x86\u201164 hosts. This includes the OpenSSL FIPS module version 3.6. No other architectures or non\u2011AVX\u2011512\u2011enabled x86\u201164 systems are impacted. The issue does not exist in TLS/DTLS protocols, which use separate cipher suites. The vulnerability only materializes when an application has an unfinished block from a previous call and the next call provides fewer bytes than required to finish it, and the input buffer ends precisely on a page boundary with the succeeding page unmapped.", "description_and_impact": "This vulnerability is an out-of-bounds read in the AES-CFB128 implementation on x86-64 systems that enable AVX\u2011512 and VAES. The over\u2011read can access up to fifteen bytes beyond the supplied input buffer when the function processes a partial block that spans a page boundary. Because the read is performed only for addresses that are not really part of the buffer, it may trigger a fault if the next page is unmapped. The fault manifests as a process crash, resulting in a denial of service. No sensitive data is disclosed because the victim does not record the read bytes.", "risk_and_exploitability": "The bug is rated CVSS 9.1, indicating high impact, yet the exploit probability is extremely low. EPSS suggests less than 1% chance of exploitation, and the vendor did not list it in KEV. In order to trigger the crash, an attacker would need to craft ciphertext that forces the decryption routine to read outside buffer bounds, a scenario that also depends on the memory layout of the victim process. Because typical applications avoid placing data on page boundaries, and because CFB mode is not used in the most common TLS implementations, the practical risk to most deployments is modest, leading the vendor to classify it as low severity."}}}}, "created": "2026-04-08T19:33:59.032687+00:00", "updated": "2026-04-13T14:26:18.258249+00:00", "vendors": ["openssl", "openssl$PRODUCT$openssl"]}