Vulnerability Description
PyJWT is a JSON Web Token implementation in Python. From 2.8.0 to 2.12.1, when verifying detached JWS tokens using the unencoded-payload option ("b64": false, RFC 7797), PyJWT performs Base64URL decoding of the compact-serialization payload segment before enforcing the detached-payload rules. For b64=false, PyJWT later discards that decoded payload and replaces it with the caller-provided detached_payload. In practice, this turns the middle segment into an attacker-controlled “work amplifier”: a remote client can supply an arbitrarily large Base64URL payload segment that forces CPU work + memory allocations even if the signature is invalid. This creates an unauthenticated DoS vector against any endpoint that verifies detached JWS using PyJWT. This vulnerability is fixed in 2.13.0.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Pyjwt Project | Pyjwt | >= 2.8.0, <= 2.12.1 |
Related Weaknesses (CWE)
References
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39ExploitMitigationVendor Advisory
- https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39ExploitMitigationVendor Advisory
FAQ
What is CVE-2026-48525?
CVE-2026-48525 is a vulnerability with a CVSS score of 5.3 (MEDIUM). PyJWT is a JSON Web Token implementation in Python. From 2.8.0 to 2.12.1, when verifying detached JWS tokens using the unencoded-payload option ("b64": false, RFC 7797), PyJWT performs Base64URL decod...
How severe is CVE-2026-48525?
CVE-2026-48525 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-48525?
Check the references section above for vendor advisories and patch information. Affected products include: Pyjwt Project Pyjwt.