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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-114616
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-22 22:18:04 UTC
Updated2026-10-22 22:18:04 UTC
DescriptionAuthlib 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.

Risk And Classification

Primary CVSS: v3.1 7.4 HIGH from [email protected]

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Problem Types: CWE-287 | CWE-326 | CWE-1391 | CWE-287 CWE-287: Improper Authentication | CWE-326 CWE-326: Inadequate Encryption Strength | CWE-1391 CWE-1391: Use of Weak Credentials

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
3.1CNADECLARED7.4HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Authlib Authlib affected < 1.9.1 Not specified

References

ReferenceSourceLinkTags
github.com/authlib/authlib/releases/tag/v1.9.1 [email protected] github.com
github.com/authlib/authlib/security/advisories/GHSA-8m4g-j4wp-wgcg [email protected] github.com
github.com/authlib/authlib/commit/4ff30db442c70e29486e1982cb0ad37c037f5f4b [email protected] github.com
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