CVE-2021-29443

jose is an npm library providing a number of cryptographic operations.

Credits

Thanks to Morgan Brown of Microsoft for bringing this up and Eva Sarafianou (@esarafianou) for helping to score this advisory.

AES_CBC_HMAC_SHA2 Algorithm (A128CBC-HS256, A192CBC-HS384, A256CBC-HS512) decryption would always execute both HMAC tag verification and CBC decryption, if either failed JWEDecryptionFailed would be thrown. But a possibly observable difference in timing when padding error would occur while decrypting the ciphertext makes a padding oracle and an adversary might be able to make use of that oracle to decrypt data without knowing the decryption key by issuing on average 128*b calls to the padding oracle (where b is the number of bytes in the ciphertext block).

CVE-2021-29443 has a CVSS score of 5.9 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.28.1, 2.0.5, 3.11.4); upgrading removes the vulnerable code path.

Kodem intelligence

All major release versions have had a patch released which ensures the HMAC tag is verified before performing CBC decryption. The fixed versions are ^1.28.1 || ^2.0.5 || >=3.11.4.

Users should upgrade their v1.x dependency to ^1.28.1, their v2.x dependency to ^2.0.5, and their v3.x dependency to ^3.11.4

1. What is CVE-2021-29443? CVE-2021-29443 is a medium-severity security vulnerability in jose (npm), affecting versions >= 1.0.0, < 1.28.1. It is fixed in 1.28.1, 2.0.5, 3.11.4.
2. How severe is CVE-2021-29443? CVE-2021-29443 has a CVSS score of 5.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of jose are affected by CVE-2021-29443? jose (npm) versions >= 1.0.0, < 1.28.1 is affected.
4. Is there a fix for CVE-2021-29443? Yes. CVE-2021-29443 is fixed in 1.28.1, 2.0.5, 3.11.4. Upgrade to this version or later.
5. Is CVE-2021-29443 exploitable, and should I be worried? Whether CVE-2021-29443 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-29443 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-29443?
   • Upgrade jose to 1.28.1 or later
   • Upgrade jose to 2.0.5 or later
   • Upgrade jose to 3.11.4 or later