Medium severity · published Oct 22, 2026
CVE-2026-114618
Authlib: Default JWT bearer grant accepts assertions for the wrong audience
New
6.8
CVSS
0.2%
EPSS
No
On KEV
Description
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.0, the default RFC 7523 JWTBearerGrant.get_audiences() returns an empty list, causing JWTBearerGrant.verify_claims() to require only that an aud claim exists without matching the current authorization server. An attacker holding a legitimate assertion for another service can present it to a server that shares the signing key and uses the default grant, obtaining an access token across a trust boundary. Implementations that override get_audiences() with the server's valid audience identifiers are not affected. This issue is fixed in version 1.9.0.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 13% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AU
authlib · authlib
< 1.9.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-114618
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-114618
github.com
https://github.com/authlib/authlib/commit/e3bd41cb29dcfee434453b135ffb487884baeedf
github.com
https://github.com/authlib/authlib/pull/945
github.com
https://github.com/authlib/authlib/releases/tag/v1.9.0
github.com
https://github.com/authlib/authlib/security/advisories/GHSA-fch4-3c6x-j4gc
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