CVE-2026-48525 Details
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.
A denial-of-service vulnerability has been identified in PyJWT, a JSON Web Token implementation in Python, affecting versions 2.8.0 through 2.12.1. The issue arises when verifying detached JWS tokens with the unencoded-payload option ('b64': false, RFC 7797). PyJWT decodes the payload segment before applying the detached-payload rules, allowing an attacker to send a large Base64URL payload that increases CPU usage and memory consumption, even with an invalid signature. This vulnerability creates an unauthenticated denial-of-service risk on endpoints that use PyJWT for detached JWS verification.
Users can upgrade to PyJWT version 2.13.0, where this vulnerability has been fixed. If detached JWS verification is not needed, tokens with 'b64' set to false can be rejected.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 28, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39 | CISA-ADP | ExploitMitigationVendor Advisory |
| https://github.com/jpadilla/pyjwt/security/advisories/GHSA-w7vc-732c-9m39 | [email protected] | ExploitMitigationVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-400 | Uncontrolled Resource Consumption | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| pyjwt project pyjwt | >= 2.8.0, <= 2.12.1 |
CPE
Remediation
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Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Jun 1, 2026 | Initial Analysis | [email protected] |
| May 28, 2026 | CVE Modified | CISA-ADP |
| May 28, 2026 | New CVE Received | [email protected] |