Vulnerability · Published Oct 22, 2026 · Assigned by GitHub_M

CVE-2026-114616Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512)

High 7.4

In plain English

A high-severity improper authentication in authlib from authlib. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 23% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.4High

Exploit odds (30 days)0.3%top 77.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.1, Authlib's OctKey.import_key() and HMAC signing and verification path accept zero-length key material. If an application's secret lookup can return an empty string or empty bytes, a remote attacker can compute the deterministic HS256, HS384, or HS512 signature for arbitrary token claims and have Authlib treat the token as authentic. This issue is fixed in version 1.9.1.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	python-authlib	no fix listed	DEBIAN-CVE-2026-114616
Debian:13	python-authlib	no fix listed	DEBIAN-CVE-2026-114616
Debian:14	python-authlib	1.9.1-1	DEBIAN-CVE-2026-114616
PyPI	authlib	1.9.1	GHSA-8m4g-j4wp-wgcg
PyPI	authlib	1.9.1	PYSEC-2026-4356
Ubuntu:26.10	python-authlib	no fix listed	UBUNTU-CVE-2026-114616

Affected products (as reported)

Vendor	Product	Versions
authlib	authlib	< 1.9.1

Weakness: CWE-287, CWE-326, CWE-1391 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References

https://github.com/authlib/authlib/security/advisories/GHSA-8m4g-j4wp-wgcg x_refsource_CONFIRM
https://github.com/authlib/authlib/commit/4ff30db442c70e29486e1982cb0ad37c037f5f4b x_refsource_MISC
https://github.com/authlib/authlib/releases/tag/v1.9.1 x_refsource_MISC