CVE-2026-48522
Description
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.
Statement
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
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.2 | N/A | 4.2 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | N/A | High |
| Privileges Required | None | N/A | None |
| User Interaction | Required | N/A | Required |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
Integrity
Technical Impact: Execute Unauthorized Code or Commands
Access Control
Technical Impact: Bypass Protection Mechanism
By providing URLs to unexpected hosts or ports, attackers can make it appear that the server is sending the request, possibly bypassing access controls such as firewalls that prevent the attackers from accessing the URLs directly. The server can be used as a proxy to conduct port scanning of hosts in internal networks, use other URLs such as that can access documents on the system (using file://), or use other protocols such as gopher:// or tftp://, which may provide greater control over the contents of requests.
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