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PyJWT CVE-2026-48522

| EUVDEUVD-2026-32915 MEDIUM
Unintended Proxy or Intermediary ('Confused Deputy') (CWE-441)
2026-05-28 GitHub_M GHSA-993g-76c3-p5m4 PYSEC-2026-175
SSRF Python Red Hat
4.2
CVSS 3.1 · GitHub Advisory
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Severity by source

GitHub Advisory PRIMARY
4.2 MEDIUM
AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
SUSE
MEDIUM
qualitative
Red Hat
4.2 MEDIUM
qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

Lifecycle Timeline

2
Patch available
May 28, 2026 - 17:01 EUVD
Analysis Generated
May 28, 2026 - 15:55 vuln.today

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 40,697 pypi packages depend on pyjwt (4,610 direct, 36,482 indirect)

Ecosystem-wide dependent count for version 2.13.0.

DescriptionGitHub Advisory

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.

AnalysisAI

PyJWKClient in PyJWT prior to 2.13.0 passes attacker-influenced URIs directly to Python's urllib.request.urlopen() without restricting URI schemes, enabling Server-Side Request Forgery (SSRF) across file://, FTP, and data-URI schemes against applications that accept untrusted jku values. Affected deployments include any Python application using PyJWKClient where the jku URL originates from a JWT header, OAuth flow parameter, or externally influenced configuration. No public exploit exists and no CISA KEV listing is present; real-world exploitation is constrained by a CVSS-confirmed high attack complexity (AC:H) and required user interaction (UI:R), making opportunistic mass exploitation unlikely.

Technical ContextAI

PyJWT is the dominant Python library for JSON Web Token creation and validation (CPE: cpe:2.3:a:jpadilla:pyjwt:*:*:*:*:*:*:*:*). PyJWKClient is its helper class for fetching JSON Web Key Sets (JWKS) from a remote URI to validate token signatures. The vulnerability arises because PyJWKClient passes the supplied uri argument directly to Python's urllib.request.urlopen(), which uses the default OpenerDirector. That director registers handlers for HTTP, HTTPS, FTP, file://, and data-URI schemes with no application-level filtering. CWE-441 (Unintended Proxy or Intermediary) precisely characterizes the root cause: PyJWKClient acts as an unrestricted intermediary fetching resources on behalf of whoever controls the URI, regardless of scheme. The library does not directly return non-HTTP(S) content to the caller, meaning simple file exfiltration requires an additional application flaw; however, side-channel behaviors (error messages, timing, DNS lookups) can still leak information about internal resources.

RemediationAI

Upgrade PyJWT to version 2.13.0, which is confirmed as the vendor-released fix per the GitHub Security Advisory GHSA-993g-76c3-p5m4 at https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4. The fix restricts PyJWKClient to HTTP and HTTPS schemes only, eliminating the file://, FTP, and data-URI attack surface. For deployments where an immediate upgrade is not possible, the most effective compensating control is to refactor the application to pass only a hardcoded, allow-listed JWKS URI to PyJWKClient rather than accepting the jku value from incoming JWT headers or external parameters; this eliminates attacker influence over the URI entirely and does not require changes to PyJWT itself. A secondary control is to apply egress network filtering that blocks the process running PyJWKClient from making non-HTTP(S) outbound connections, mitigating FTP and local file access at the network layer without addressing the root cause. Neither workaround substitutes for patching, as both introduce operational complexity and leave the underlying unfiltered call intact.

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Vendor StatusVendor

SUSE

Severity: Medium
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 12 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Micro 5.5 Fixed
SUSE Linux Enterprise Module for Basesystem 15 SP7 Fixed

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CVE-2026-48522 vulnerability details – vuln.today
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