High severity · published Oct 22, 2026
CVE-2026-114616
Authlib accepts an empty HMAC key, allowing JWS/JWT signature forgery (HS256/HS384/HS512)
New
7.4
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 11% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AU
authlib · authlib
< 1.9.1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-114616
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-114616
github.com
https://github.com/authlib/authlib/commit/4ff30db442c70e29486e1982cb0ad37c037f5f4b
github.com
https://github.com/authlib/authlib/releases/tag/v1.9.1
github.com
https://github.com/authlib/authlib/security/advisories/GHSA-8m4g-j4wp-wgcg
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