CVE-2026-48522

PyJWKClient: missing scheme allowlist enables SSRF + token forgery via file://, ftp://, data: schemes

Published May 28, 2026 CVSS 3.1 · 4.2 Medium EPSS < 1% KEV · Not listed
Description
PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient passes its uri argument directly to urllib.request.urlopen() which uses Python stdlib's default OpenerDirector registering HTTPHandler, HTTPSHandler, FTPHandler, FileHandler, and DataHandler. There is currently no documented option to restrict which schemes PyJWKClient will fetch. If an application's jku URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can cause PyJWKClient to read arbitrary local files via file:// (SSRF on local filesystem), cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface), or forge tokens that PyJWT verifies as valid. The library does not directly return non-HTTP(S) URI contents to the attacker; the chained "plant a JWKS to forge tokens" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. This vulnerability is fixed in 2.13.0.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-993g-76c3-p5m4 PyJWKClient: missing scheme allowlist enables CVE-2024-21643-class SSRF + token forgery via file://, ftp://, data: schemes
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Pyjwt Project
Pyjwt Project pyjwt
CPEs cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:*
Vendors & Products Pyjwt Project
Pyjwt Project pyjwt
Type Values Removed Values Added
First Time appeared Jpadilla
Jpadilla pyjwt
Vendors & Products Jpadilla
Jpadilla pyjwt
Type Values Removed Values Added
Description PyJWT is a JSON Web Token implementation in Python. Prior to 2.13.0, PyJWKClient passes its uri argument directly to urllib.request.urlopen() which uses Python stdlib's default OpenerDirector registering HTTPHandler, HTTPSHandler, FTPHandler, FileHandler, and DataHandler. There is currently no documented option to restrict which schemes PyJWKClient will fetch. If an application's jku URL ingestion path accepts attacker-influenced URLs (e.g., from JWT header, configuration file, OAuth flow parameter), the attacker can cause PyJWKClient to read arbitrary local files via file:// (SSRF on local filesystem), cause PyJWKClient to attempt FTP / data-URI fetches (broader SSRF surface), or forge tokens that PyJWT verifies as valid. The library does not directly return non-HTTP(S) URI contents to the attacker; the chained "plant a JWKS to forge tokens" scenario described in the original report requires additional application-layer flaws (attacker write access to a filesystem path, untrusted jku derivation) that this fix does not address. This vulnerability is fixed in 2.13.0.
Title PyJWKClient: missing scheme allowlist enables SSRF + token forgery via file://, ftp://, data: schemes
Weaknesses CWE-441
CWE-918
References
Metrics cvssV3_1

{'score': 4.2, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jun 2, 2026, 3:47 PM
Reserved
May 21, 2026, 4:18 PM
Status
Modified
Published
May 28, 2026, 4:16 PM
Modified
Oct 26, 2026, 1:10 PM
Severity
Moderate
Public date
May 28, 2026, 3:00 PM