{"id":"CVE-2026-53939","state":"PUBLISHED","title":"OpenIDC/cjose uses all-zero Content Encryption Key for AES-CBC-HMAC JWE encryption","description":"OpenIDC/cjose is a C library implementing the Javascript Object Signing and Encryption (JOSE). In versions 0.6.1 through 0.6.2.5, when cjose encrypts a JWE using an AES-CBC-HMAC content-encryption algorithm (`A128CBC-HS256`, `A192CBC-HS384`, or `A256CBC-HS512`) together with any key-management algorithm that generates a fresh content-encryption key (CEK), the CEK is all zero bytes instead of being randomly generated. The resulting JWE is therefore encrypted and authenticated under a fixed, publicly known key, so anyone who obtains the JWE can recover the plaintext and forge or modify the content. This is fixed in version 0.6.2.6 by `_cjose_jwe_set_cek_aes_cbc()` generating the CEK from `RAND_bytes`. A regression test asserts that the `encrypted_key` differs across two encryptions for each AES-CBC-HMAC variant. Until upgrading, for data encrypted with cjose, three options are available. Use an AES-GCM `enc` (`A128GCM` / `A192GCM` / `A256GCM`) instead of an AES-CBC-HMAC `enc`,  use `alg=dir` with a caller-supplied CEK, or avoid using cjose for JWE encryption with the affected algorithm pair. These are mitigations for new ciphertexts only; data already encrypted under the zero key remains compromised and should be re-encrypted (and any secrets it contained rotated).","publishedAt":"2026-09-08T23:36:13.668Z","updatedAt":"2026-09-09T15:12:15.459Z","severity":{"score":9.1,"label":"Critical","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["OpenIDC cjose"],"affected":[{"vendor":"OpenIDC","product":"cjose","versions":[{"version":">= 0.6.1, < 0.6.2.6","status":"affected"}]}],"references":["https://github.com/OpenIDC/cjose/security/advisories/GHSA-f6wf-pqg3-6wqq","https://github.com/OpenIDC/cjose/commit/2a6e5bd969fa20059fb00913fb9f57d77ea6a4d9","https://github.com/OpenIDC/cjose/releases/tag/v0.6.2.6"],"weaknesses":["CWE-321","CWE-330"],"ingestedAt":"2026-10-29T20:12:16.098Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/53xxx/CVE-2026-53939.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-53939","state":"PUBLISHED","datePublished":"2026-09-08T23:36:13.668Z","dateUpdated":"2026-09-09T15:12:15.459Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-06-11T15:46:12.318Z"},"containers":{"cna":{"title":"OpenIDC/cjose uses all-zero Content Encryption Key for AES-CBC-HMAC JWE encryption","descriptions":[{"lang":"en","value":"OpenIDC/cjose is a C library implementing the Javascript Object Signing and Encryption (JOSE). In versions 0.6.1 through 0.6.2.5, when cjose encrypts a JWE using an AES-CBC-HMAC content-encryption algorithm (`A128CBC-HS256`, `A192CBC-HS384`, or `A256CBC-HS512`) together with any key-management algorithm that generates a fresh content-encryption key (CEK), the CEK is all zero bytes instead of being randomly generated. The resulting JWE is therefore encrypted and authenticated under a fixed, publicly known key, so anyone who obtains the JWE can recover the plaintext and forge or modify the content. This is fixed in version 0.6.2.6 by `_cjose_jwe_set_cek_aes_cbc()` generating the CEK from `RAND_bytes`. A regression test asserts that the `encrypted_key` differs across two encryptions for each AES-CBC-HMAC variant. Until upgrading, for data encrypted with cjose, three options are available. Use an AES-GCM `enc` (`A128GCM` / `A192GCM` / `A256GCM`) instead of an AES-CBC-HMAC `enc`,  use `alg=dir` with a caller-supplied CEK, or avoid using cjose for JWE encryption with the affected algorithm pair. These are mitigations for new ciphertexts only; data already encrypted under the zero key remains compromised and should be re-encrypted (and any secrets it contained rotated)."}],"affected":[{"vendor":"OpenIDC","product":"cjose","versions":[{"version":">= 0.6.1, < 0.6.2.6","status":"affected"}]}],"references":[{"url":"https://github.com/OpenIDC/cjose/security/advisories/GHSA-f6wf-pqg3-6wqq","name":"https://github.com/OpenIDC/cjose/security/advisories/GHSA-f6wf-pqg3-6wqq","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/OpenIDC/cjose/commit/2a6e5bd969fa20059fb00913fb9f57d77ea6a4d9","name":"https://github.com/OpenIDC/cjose/commit/2a6e5bd969fa20059fb00913fb9f57d77ea6a4d9","tags":["x_refsource_MISC"]},{"url":"https://github.com/OpenIDC/cjose/releases/tag/v0.6.2.6","name":"https://github.com/OpenIDC/cjose/releases/tag/v0.6.2.6","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"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"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-321","lang":"en","description":"CWE-321: Use of Hard-coded Cryptographic Key","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-330","lang":"en","description":"CWE-330: Use of Insufficiently Random Values","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-09-08T23:36:13.668Z"},"source":{"advisory":"GHSA-f6wf-pqg3-6wqq","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/OpenIDC/cjose/security/advisories/GHSA-f6wf-pqg3-6wqq","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-09T15:12:10.094529Z","id":"CVE-2026-53939","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"total"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-09T15:12:15.459Z"}}]}}}