{"id":"CVE-2026-49852","state":"PUBLISHED","title":"joserfc: HS256/HS384/HS512 verify accepts empty/nil HMAC key (cross-language sibling of CVE-2026-45363)","description":"joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.6.8, joserfc.jwt.decode accepts attacker-forged HMAC-signed tokens when the caller-supplied verification key is the empty string or None, because HMACAlgorithm.sign and HMACAlgorithm.verify in src/joserfc/_rfc7518/jws_algs.py pass the output of OctKey.get_op_key(...) to hmac.new(...) and OctKey.import_key in src/joserfc/_rfc7518/oct_key.py only emits a SecurityWarning for keys shorter than 14 bytes without rejecting zero-length input. This issue is fixed in version 1.6.8.","publishedAt":"2026-07-17T19:14:58.019Z","updatedAt":"2026-07-20T14:58:41.701Z","severity":{"score":8.7,"label":"High","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["authlib joserfc"],"affected":[{"vendor":"authlib","product":"joserfc","versions":[{"version":"< 1.6.8","status":"affected"}]}],"references":["https://github.com/authlib/joserfc/security/advisories/GHSA-gg9x-qcx2-xmrh","https://github.com/authlib/joserfc/commit/86d00910b2b2d2d07503fee9b572906daefab7f1","https://github.com/authlib/joserfc/releases/tag/1.6.8"],"weaknesses":["CWE-287","CWE-326","CWE-1391"],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/49xxx/CVE-2026-49852.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-49852","state":"PUBLISHED","datePublished":"2026-07-17T19:14:58.019Z","dateUpdated":"2026-07-20T14:58:41.701Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-06-01T22:03:19.640Z"},"containers":{"cna":{"title":"joserfc: HS256/HS384/HS512 verify accepts empty/nil HMAC key (cross-language sibling of CVE-2026-45363)","descriptions":[{"lang":"en","value":"joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.6.8, joserfc.jwt.decode accepts attacker-forged HMAC-signed tokens when the caller-supplied verification key is the empty string or None, because HMACAlgorithm.sign and HMACAlgorithm.verify in src/joserfc/_rfc7518/jws_algs.py pass the output of OctKey.get_op_key(...) to hmac.new(...) and OctKey.import_key in src/joserfc/_rfc7518/oct_key.py only emits a SecurityWarning for keys shorter than 14 bytes without rejecting zero-length input. This issue is fixed in version 1.6.8."}],"affected":[{"vendor":"authlib","product":"joserfc","versions":[{"version":"< 1.6.8","status":"affected"}]}],"references":[{"url":"https://github.com/authlib/joserfc/security/advisories/GHSA-gg9x-qcx2-xmrh","name":"https://github.com/authlib/joserfc/security/advisories/GHSA-gg9x-qcx2-xmrh","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/authlib/joserfc/commit/86d00910b2b2d2d07503fee9b572906daefab7f1","name":"https://github.com/authlib/joserfc/commit/86d00910b2b2d2d07503fee9b572906daefab7f1","tags":["x_refsource_MISC"]},{"url":"https://github.com/authlib/joserfc/releases/tag/1.6.8","name":"https://github.com/authlib/joserfc/releases/tag/1.6.8","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":8.7,"baseSeverity":"HIGH","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-287","lang":"en","description":"CWE-287: Improper Authentication","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-326","lang":"en","description":"CWE-326: Inadequate Encryption Strength","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-1391","lang":"en","description":"CWE-1391: Use of Weak Credentials","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-07-17T19:14:58.019Z"},"source":{"advisory":"GHSA-gg9x-qcx2-xmrh","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/authlib/joserfc/security/advisories/GHSA-gg9x-qcx2-xmrh","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-20T14:58:30.595996Z","id":"CVE-2026-49852","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-07-20T14:58:41.701Z"}}]}}}