CVE-2026-48522: pyjwt SSRF — Exploit & Fix

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.

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CVSS v3.1 Score

4.2

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N

EPSS — Exploit Prediction

0.0015

Probability of exploitation

0.04%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-441 CWE-441

CWE-918 Server-Side Request Forgery (SSRF)

Affected Products

Vendor	Product	Versions
pyjwt_project	pyjwt	< 2.13.0

References

Advisories & Patches

https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4 https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4

Exploits

https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4 https://github.com/jpadilla/pyjwt/security/advisories/GHSA-993g-76c3-p5m4

Frequently Asked Questions

What is CVE-2026-48522? +

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. It has a CVSS v3.1 base score of 4.2 (MEDIUM).

How severe is CVE-2026-48522? +

CVE-2026-48522 has a CVSS v3.1 score of 4.2 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0015, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-48522? +

CVE-2026-48522 affects products from pyjwt_project, specifically: pyjwt. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-48522? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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