Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.5, Authlib’s JOSE implementation accepts unbounded JWS/JWT header and signature segments. A remote attacker can craft a token whose base64url‑encoded header or signature spans hundreds of megabytes. During verification, Authlib decodes and parses the full input before it is rejected, driving CPU and memory consumption to hostile levels and enabling denial of service. Version 1.6.5 patches the issue. Some temporary workarounds are available. Enforce input size limits before handing tokens to Authlib and/or use application-level throttling to reduce amplification risk.
Metrics
Affected Vendors & Products
References
History
Mon, 20 Oct 2025 16:45:00 +0000
| Type | Values Removed | Values Added |
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| CPEs | cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:* |
Mon, 20 Oct 2025 16:30:00 +0000
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| First Time appeared |
Authlib
Authlib authlib |
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| Vendors & Products |
Authlib
Authlib authlib |
Sat, 11 Oct 2025 00:15:00 +0000
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| References |
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| Metrics |
threat_severity
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threat_severity
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Fri, 10 Oct 2025 21:15:00 +0000
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| Metrics |
ssvc
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Fri, 10 Oct 2025 19:30:00 +0000
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| Description | Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.5, Authlib’s JOSE implementation accepts unbounded JWS/JWT header and signature segments. A remote attacker can craft a token whose base64url‑encoded header or signature spans hundreds of megabytes. During verification, Authlib decodes and parses the full input before it is rejected, driving CPU and memory consumption to hostile levels and enabling denial of service. Version 1.6.5 patches the issue. Some temporary workarounds are available. Enforce input size limits before handing tokens to Authlib and/or use application-level throttling to reduce amplification risk. | |
| Title | Authlib is vulnerable to Denial of Service via Oversized JOSE Segments | |
| Weaknesses | CWE-20 CWE-400 CWE-770 |
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| References |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published: 2025-10-10T19:25:07.679Z
Updated: 2025-10-10T20:47:08.736Z
Reserved: 2025-10-03T22:21:59.615Z
Link: CVE-2025-61920
Updated: 2025-10-10T20:47:02.479Z
Status : Analyzed
Published: 2025-10-10T20:15:37.893
Modified: 2025-10-20T16:39:59.980
Link: CVE-2025-61920