CVE-2021-29444
Padding Oracle Attack due to Observable Timing Discrepancy in jose-browser-runtime
Description
### Impact [AES_CBC_HMAC_SHA2 Algorithm](https://tools.ietf.org/html/rfc7518#section-5.2) (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). ### Patches 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`. ### Credits Thanks to Morgan Brown of Microsoft for bringing this up and Eva Sarafianou (@esarafianou) for helping to score this advisory.
How to fix CVE-2021-29444
To remediate CVE-2021-29444, upgrade the affected package to a fixed version below.
- —upgrade to 3.11.4 or later
Is CVE-2021-29444 being exploited?
Low — EPSS is 0.4%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 3.11.4
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM5.9 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N |