Authlib is vulnerable to Denial of Service via Oversized JOSE Segments (authlib authlib)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.64 % · percentile 51 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Modified
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.
Weaknesses (CWE)
- CWE-20 — Improper Input Validation
- CWE-400 — Uncontrolled Resource Consumption
- CWE-770 — Allocation of Resources Without Limits or Throttling
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | GitHub_M |
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | NVD · security-advisories@github.com (Secondary) |
Advisories
- GHSA-pq5p-34cr-23v9 — Authlib is vulnerable to Denial of Service via Oversized JOSE Segments
- PYSEC-2026-1203 — Authlib is vulnerable to Denial of Service via Oversized JOSE Segments
European references
- ENISA EUVD · EUVD-2025-33768
- GCVE · GCVE-0-2025-61920
Affected configurations (NVD CPE)
cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:*< 1.6.5
Affected products
| Product | Versions |
|---|---|
| authlib · authlib | affected < 1.6.5 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |