{"api_version":"1","generated_at":"2026-04-18T11:23:44+00:00","cve":"CVE-2026-34876","urls":{"html":"https://cve.report/CVE-2026-34876","api":"https://cve.report/api/cve/CVE-2026-34876.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-34876","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-34876"},"summary":{"title":"CVE-2026-34876","description":"An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in mbedtls_ccm_finish() in library/ccm.c allows attackers to obtain adjacent CCM context data via invocation of the multipart CCM API with an oversized tag_len parameter. This is caused by missing validation of the tag_len parameter against the size of the internal 16-byte authentication buffer. The issue affects the public multipart CCM API in Mbed TLS 3.x, where mbedtls_ccm_finish() can be invoked directly by applications. In Mbed TLS 4.x versions prior to the fix, the same missing validation exists in the internal implementation; however, the function is not exposed as part of the public API. Exploitation requires application-level invocation of the multipart CCM API.","state":"PUBLISHED","assigner":"mitre","published_at":"2026-04-02 16:16:26","updated_at":"2026-04-07 12:14:22"},"problem_types":["CWE-125","n/a","CWE-125 CWE-125 Out-of-bounds Read"],"metrics":[{"version":"3.1","source":"ADP","type":"DECLARED","score":"7.5","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","data":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.5,"baseSeverity":"HIGH","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:N","version":"3.1"}},{"version":"3.1","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","type":"Secondary","score":"7.5","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"NONE"}}],"references":[{"url":"https://mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/","name":"https://mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/","refsource":"cve@mitre.org","tags":["Vendor Advisory"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ccm-finish-boundary-check/","name":"https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ccm-finish-boundary-check/","refsource":"cve@mitre.org","tags":["Vendor Advisory"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-34876","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34876","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"n/a","product":"n/a","version":"affected n/a","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[{"cve_year":"2026","cve_id":"34876","vulnerable":"1","versionEndIncluding":"","cpe1":"cpe","cpe2":"2.3","cpe3":"a","cpe4":"arm","cpe5":"mbed_tls","cpe6":"*","cpe7":"*","cpe8":"*","cpe9":"*","cpe10":"*","cpe11":"*","cpe12":"*","cpe13":"*"}],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"34876","cve":"CVE-2026-34876","epss":"0.000150000","percentile":"0.033840000","score_date":"2026-04-07","updated_at":"2026-04-08 00:03:39"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":7.5,"baseSeverity":"HIGH","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:N","version":"3.1"}},{"other":{"content":{"id":"CVE-2026-34876","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","timestamp":"2026-04-02T15:53:54.288854Z","version":"2.0.3"},"type":"ssvc"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-125","description":"CWE-125 Out-of-bounds Read","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-04-02T15:54:45.230Z","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP"},"title":"CISA ADP Vulnrichment"}],"cna":{"affected":[{"product":"n/a","vendor":"n/a","versions":[{"status":"affected","version":"n/a"}]}],"descriptions":[{"lang":"en","value":"An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in mbedtls_ccm_finish() in library/ccm.c allows attackers to obtain adjacent CCM context data via invocation of the multipart CCM API with an oversized tag_len parameter. This is caused by missing validation of the tag_len parameter against the size of the internal 16-byte authentication buffer. The issue affects the public multipart CCM API in Mbed TLS 3.x, where mbedtls_ccm_finish() can be invoked directly by applications. In Mbed TLS 4.x versions prior to the fix, the same missing validation exists in the internal implementation; however, the function is not exposed as part of the public API. Exploitation requires application-level invocation of the multipart CCM API."}],"problemTypes":[{"descriptions":[{"description":"n/a","lang":"en","type":"text"}]}],"providerMetadata":{"dateUpdated":"2026-04-02T15:08:59.859Z","orgId":"8254265b-2729-46b6-b9e3-3dfca2d5bfca","shortName":"mitre"},"references":[{"url":"https://mbed-tls.readthedocs.io/en/latest/tech-updates/security-advisories/"},{"url":"https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ccm-finish-boundary-check/"}]}},"cveMetadata":{"assignerOrgId":"8254265b-2729-46b6-b9e3-3dfca2d5bfca","assignerShortName":"mitre","cveId":"CVE-2026-34876","datePublished":"2026-04-02T00:00:00.000Z","dateReserved":"2026-03-31T00:00:00.000Z","dateUpdated":"2026-04-02T15:54:45.230Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-04-02 16:16:26","lastModifiedDate":"2026-04-07 12:14:22","problem_types":["CWE-125","n/a","CWE-125 CWE-125 Out-of-bounds Read"],"metrics":{"cvssMetricV31":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N","baseScore":7.5,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"NONE"},"exploitabilityScore":3.9,"impactScore":3.6}]},"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:arm:mbed_tls:*:*:*:*:*:*:*:*","versionStartIncluding":"3.1.0","versionEndExcluding":"3.6.6","matchCriteriaId":"11EB1D49-E6D0-407C-9798-C7E631B1A03D"}]}]}]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"34876","Ordinal":"1","Title":"CVE-2026-34876","CVE":"CVE-2026-34876","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"34876","Ordinal":"1","NoteData":"An issue was discovered in Mbed TLS 3.x before 3.6.6. An out-of-bounds read vulnerability in mbedtls_ccm_finish() in library/ccm.c allows attackers to obtain adjacent CCM context data via invocation of the multipart CCM API with an oversized tag_len parameter. This is caused by missing validation of the tag_len parameter against the size of the internal 16-byte authentication buffer. The issue affects the public multipart CCM API in Mbed TLS 3.x, where mbedtls_ccm_finish() can be invoked directly by applications. In Mbed TLS 4.x versions prior to the fix, the same missing validation exists in the internal implementation; however, the function is not exposed as part of the public API. Exploitation requires application-level invocation of the multipart CCM API.","Type":"Description","Title":"CVE-2026-34876"}]}}}