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Vulnerability record · CVE-2026-48525 · published 28 May 2026

CVE-2026-48525: Pyjwt project pyjwt uncontrolled resource consumption vulnerability

Pyjwt Project · Pyjwt

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.

5.3 CVSS 3.1 Medium EPSS 0.42% · top 66.7% CWE-400 · Uncontrolled resource consumption
5.3CVSS 3.1 base score
0.42%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39 ExploitMitigationVendor Advisory
https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39 ExploitMitigationVendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2026-48525), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.