CVE-2026-53939
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).
INFO
Published Date :
Sept. 9, 2026, 12:17 a.m.
Last Modified :
Sept. 9, 2026, 12:17 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-53939
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | CRITICAL | [email protected] |
Solution
- Upgrade cjose to version 0.6.2.6 or later.
- Use AES-GCM encryption instead of AES-CBC-HMAC.
- Use alg=dir with a caller-supplied CEK.
- Re-encrypt affected data and rotate secrets.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-53939.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-53939 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-53939
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-53939 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-53939 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Sep. 09, 2026
Action Type Old Value New Value Added 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). Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N Added CWE CWE-330 Added CWE CWE-321 Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/53xxx/CVE-2026-53939.json">CVE-2026-53939</a> Added Reference https://github.com/OpenIDC/cjose/commit/2a6e5bd969fa20059fb00913fb9f57d77ea6a4d9 Added Reference https://github.com/OpenIDC/cjose/releases/tag/v0.6.2.6 Added Reference https://github.com/OpenIDC/cjose/security/advisories/GHSA-f6wf-pqg3-6wqq