PT-2026-44397 · Jpadilla · Pyjwt

Published 2026-05-28 · Updated 2026-05-28 · CVE-2026-48525

Mitre

CVSS v3.1

5.3

Medium

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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.

Exploit

Fix

Resource Exhaustion

Weakness Enumeration

CWE-400

Related Identifiers

CVE-2026-48525

Affected Products

Pyjwt

References · 2

• 🔥 https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39 · Exploit
• https://nvd.nist.gov/vuln/detail/CVE-2026-48525 · Security Note