CVE-2026-53939: CWE-321: Use of Hard-coded Cryptographic Key in OpenIDC cjose
Affects OpenIDC cjoseSource CVE Database V5
Not known to be exploited · CVSS 9.1 Critical · patch available : patch OpenIDC cjose as a priority.
Data as of 10/24/2026, 17:08:26 UTC
- Exploitation
Not in CISA KEV, no exploitation reported
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 14% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NWhat to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| OpenIDCcjose | Affected
| Fixed in– |
GitHub Actionsopenidc/cjosepkg:github/openidc/cjoseOther threats | Affected
| Fixed in– |
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AI-suggested
A patch is available in OpenIDC cjose version 0.6.2.6 which fixes the CEK generation to use secure random bytes. Users should upgrade to version 0.6.2.6 or later. Until upgrading, mitigations for new ciphertexts include using AES-GCM content-encryption algorithms instead of AES-CBC-HMAC, using the 'alg=dir' option with a caller-supplied CEK, or avoiding cjose for JWE encryption with the affected algorithm pairs. Data encrypted with vulnerable versions should be re-encrypted and any secrets rotated. Since this is a library, users must apply the fix in their deployments. No known exploits in the wild have been reported.
Description
OpenIDC cjose versions 0.6.1 through 0.6.2.5 contain a critical vulnerability where the content-encryption key (CEK) used in AES-CBC-HMAC algorithms is hard-coded to all zero bytes instead of being randomly generated. This flaw allows anyone with access to the encrypted JSON Web Encryption (JWE) token to decrypt and modify its contents. The issue is fixed in version 0.6.2.6 by properly generating the CEK using a secure random function. Until upgrading, mitigations include using AES-GCM encryption, supplying a CEK directly, or avoiding the affected encryption algorithms. Data encrypted with the vulnerable versions should be re-encrypted and secrets rotated.
Impact
The vulnerability allows attackers to decrypt and modify encrypted JWE tokens because the CEK is fixed and publicly known (all zero bytes). This compromises confidentiality and integrity of the encrypted data. The CVSS score of 9.1 reflects critical impact with network attack vector, low complexity, no privileges or user interaction required, and high confidentiality and integrity impact. Availability is not affected.