CVE-2026-48525

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.

How to fix CVE-2026-48525

To remediate CVE-2026-48525, upgrade the affected package to a fixed version below.

• —no fix listed
• —upgrade to 2.13.0 or later

Is CVE-2026-48525 being exploited?

Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0
• >= 2.8.0, < 2.13.0

CVSS scores

References (2)

• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2026-48525
• EXPLOITgithub.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39