Padding Oracle Attack due to Observable Timing Discrepancy in jose-node-esm-runtime

published 2021-04-16 5 y ago modified 2026-07-08 4 mo ago also GHSA-4v4g-726h-xvfv , EUVD-2021-0760

cvss: 5.9; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 1.1%; EPSS 1.1% chance of exploitation in 30 days, percentile 65%
public exploits: 0; none known

jose-node-esm-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`.

Patch / fix

fixed in 2

npm jose-node-esm-runtime 3.11.4
jose-node-cjs-runtime_project jose-node-cjs-runtime 3.11.4

Exploit prediction

1.07% chance of exploitation in the next 30 days, higher than 65% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD	2.0	4.3	AV:N/AC:M/Au:N/C:P/I:N/A:N
GitHub	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	jose-node-esm-runtime	<3.11.4	3.11.4

Affected products

panva jose-node-esm-runtime

Classification

Weakness

CWE-203 Observable Discrepancy
CWE-208 Observable Timing Discrepancy
CWE-696 Incorrect Behavior Order

References

github.com /panva/jose/security/advisories/GHSA-4v4g-726h-xvfv
web, third-party-advisory
npmjs.com /package/jose-node-esm-runtime
web, product, third-party-advisory
nvd.nist.gov /vuln/detail/CVE-2021-29445
advisory
github.com /panva/jose
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary