High 8.7Published Jul 17, 2026

CVE-2026-49852joserfc: HS256/HS384/HS512 verify accepts empty/nil HMAC key (cross-language sibling of CVE-2026-45363)

Updated under an hour ago (Oct 27, 2026, 5:10 AM ET)

Does this affect you?

It affects authlib joserfc. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for authlib joserfc

Exploited in the last 30 days

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.6.8, joserfc.jwt.decode accepts attacker-forged HMAC-signed tokens when the caller-supplied verification key is the empty string or None, because HMACAlgorithm.sign and HMACAlgorithm.verify in src/joserfc/_rfc7518/jws_algs.py pass the output of OctKey.get_op_key(...) to hmac.new(...) and OctKey.import_key in src/joserfc/_rfc7518/oct_key.py only emits a SecurityWarning for keys shorter than 14 bytes without rejecting zero-length input. This issue is fixed in version 1.6.8.

CVSS: 8.7 HIGH (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Weakness (CWE): CWE-287, CWE-326, CWE-1391
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Jul 20, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

authlib joserfc authlib:joserfc (from the name)	before 1.6.8	CNA record

References

References

https://github.com/authlib/joserfc/security/advisories/GHSA-gg9x-qcx2-xmrh	x-refsource-confirm
https://github.com/authlib/joserfc/commit/86d00910b2b2d2d07503fee9b572906daefab7f1	x-refsource-misc
https://github.com/authlib/joserfc/releases/tag/1.6.8	x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.