Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-05-28T15:00:30 python-pyjwt: PyJWT: Server-Side Request Forgery (SSRF) via uncontrolled URL fetching in PyJWKClient 4.2 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N CWE-918

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.

A flaw was found in PyJWT, a JSON Web Token implementation in Python. The `PyJWKClient` component, prior to version 2.13.0, directly passes its Uniform Resource Identifier (URI) argument to `urllib.request.urlopen()`. This allows a remote attacker, by influencing the application's `jku` URL ingestion path, to perform Server-Side Request Forgery (SSRF) attacks, potentially leading to the reading of arbitrary local files or broader network access. This vulnerability could also enable attackers to forge tokens that PyJWT verifies as legitimate.

This Moderate severity vulnerability in PyJWT's `PyJWKClient` component allows for Server-Side Request Forgery (SSRF) if an application processes attacker-controlled `jku` URLs. While the flaw enables reading local files or broader network access, successful token forging requires additional application-layer vulnerabilities, such as untrusted `jku` derivation or attacker write access to a filesystem path. Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. 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rhelai3/bootc-gaudi-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Fix deferred rhelai3/bootc-gcp-cuda-rhel9 Red Hat Enterprise Linux AI (RHEL AI) 3 Not affected rhelai3/bootc-rocm-rhel9 Red Hat Hardened Images Not affected llvm Red Hat Hardened Images Not affected llvm21 Red Hat Hardened Images Affected rust Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-feature-server-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-kserve-agent-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-kserve-controller-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-kserve-router-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-kserve-storage-initializer-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-llama-stack-core-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-llm-d-kv-cache-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred rhoai/odh-model-registry-job-async-upload-rhel9 Red Hat OpenShift AI (RHOAI) Fix deferred 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Infrastructure 4 for Cloud Providers Fix deferred python-pyjwt https://www.cve.org/CVERecord?id=CVE-2026-48522 https://nvd.nist.gov/vuln/detail/CVE-2026-48522 https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4