{"id":"CVE-2026-53939","title":"OpenIDC/cjose is a C library implementing the Javascript Object Signing and Encryption (JOSE)","summary":"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-HS3…","severity":"critical","cvss":9.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","cwe":["CWE-321","CWE-330"],"vendor":"OpenIDC","product":"cjose","affected":["cjose >= 0.6.1, < 0.6.2.6"],"published":"2026-09-09","updated":"2026-09-10","sourceUpdated":"2026-09-10T19:57:48.533","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-53939","references":[{"url":"https://github.com/OpenIDC/cjose/commit/2a6e5bd969fa20059fb00913fb9f57d77ea6a4d9","label":"security-advisories@github.com"},{"url":"https://github.com/OpenIDC/cjose/releases/tag/v0.6.2.6","label":"security-advisories@github.com"},{"url":"https://github.com/OpenIDC/cjose/security/advisories/GHSA-f6wf-pqg3-6wqq","label":"security-advisories@github.com"},{"url":"https://github.com/OpenIDC/cjose/security/advisories/GHSA-f6wf-pqg3-6wqq","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}],"tags":["nvd","cve.org","exploit-available"],"epss":0.00196,"epssPercentile":0.0964,"exploitAvailable":true,"ssvc":{"exploitation":"poc","automatable":"yes","technicalImpact":"total","timestamp":"2026-09-09T15:12:10.094529Z"},"ingestedAt":"2026-09-09T00:15:28.907Z","slug":"CVE-2026-53939","body":"## Overview\n\nOpenIDC/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).\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version 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