CVE-2021-29446: 
JavaScript vulnerability analysis and mitigation

A padding oracle vulnerability (CVE-2021-29446) was discovered in jose-node-cjs-runtime versions prior to 3.11.4. The vulnerability affects the AESCBCHMAC_SHA2 Algorithm (A128CBC-HS256, A192CBC-HS384, A256CBC-HS512) decryption process, where observable timing differences during padding error occurrence could be exploited (GitHub Advisory).

The vulnerability stems from the implementation of AESCBCHMAC_SHA2 Algorithm decryption, where both HMAC tag verification and CBC decryption would always execute. When either operation failed, a JWEDecryptionFailed error would be thrown. However, the timing discrepancy during padding errors could be observed and exploited as a padding oracle (GitHub Advisory). The vulnerability has been assigned a CVSS v3.1 base score of 5.9 (High) with the vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.

An adversary could potentially exploit this vulnerability to decrypt data without knowing the decryption key. The attack would require on average 128*b calls to the padding oracle, where b represents the number of bytes in the ciphertext block (GitHub Advisory).

The vulnerability has been patched in version 3.11.4 and later. The fix ensures that HMAC tag verification is performed before CBC decryption. Users are advised to upgrade to version 3.11.4 or later (GitHub Advisory).