CVE-2021-29444: Padding Oracle Attack due to Observable Timing Discrepancy in jose-browser-runtime

Vulnerability summary

CVE-2021-29444 is a medium (CVSS 5.9) Observable Discrepancy vulnerability in jose-node-cjs-runtime_project jose-node-cjs-runtime. EPSS estimates a 1.07% chance of exploitation in the next 30 days, higher than 64.8% of scored vulnerabilities.

Timeline

1. 16-04-2021
   PublishedVulnerability first disclosed.
2. 03-08-2024
   Last modifiedVulnerability information updated.

Description

jose-browser-runtime is an npm package which provides a number of cryptographic functions. In versions prior to 3.11.4 the 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). A patch was released which ensures the HMAC tag is verified before performing CBC decryption. The fixed versions are `>=3.11.4`. Users should upgrade to `^3.11.4`.

• CWE-203Observable DiscrepancyThe product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.