CVE-2026-53939 (GCVE-0-2026-53939)
Vulnerability from cvelistv5 – Published: 2026-09-08 23:36 – Updated: 2026-09-09 15:12
VLAI
EPSS
VEX
Title
OpenIDC/cjose uses all-zero Content Encryption Key for AES-CBC-HMAC JWE encryption
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-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).
Severity
9.1 (Critical)
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-09 15:12 UTC
Assigner
GitHub_M
CNA
References
3 references
| URL | Tags |
|---|---|
| https://github.com/OpenIDC/cjose/security/advisor… | x_refsource_CONFIRM |
| https://github.com/OpenIDC/cjose/commit/2a6e5bd96… | x_refsource_MISC |
| https://github.com/OpenIDC/cjose/releases/tag/v0.6.2.6 | x_refsource_MISC |
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Browse all ATT&CK techniques and the vulnerabilities related to each.
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