PyJWT: PyJWKClient follows redirects when fetching JWKSGHSA-9v7f-9g4p-ffgj
HIGHFix: jpadilla/pyjwt@0a795b8GHSA-9v7f-9g4p-ffgj is a high-severity (CVSS 7.4) Information Exposure vulnerability in pyjwt. A fix is available for pyjwt — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-9v7f-9g4p-ffgj.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-9v7f-9g4p-ffgj by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 383,485 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
pyjwtReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
PyJWT 2.13.0 PyJWKClient followed HTTP redirects while fetching a JWKS,
without validating the redirect destination. A configured trusted endpoint
could therefore redirect the client to a different host.
Impact
When an application uses PyJWKClient with caller-supplied request headers and
an attacker can influence the configured endpoint's response, the redirected
request could expose those headers and the redirected response could be used as
authoritative key material. This could cause JWKS trust poisoning and, in
affected mixed-configuration applications, forged JWT acceptance. The issue
requires an attacker-influenced redirect from the configured JWKS endpoint; it
is not triggered by a token kid alone.
Affected versions
PyJWT <= 2.13.0.
Fix
The issue is fixed on master in commit
0a795b8e1f6ef08f634aa7086fc41cc6d5ce3e56.
PyJWKClient now disables automatic redirects for JWKS fetches. Regression
tests verify that a redirect is rejected without contacting its destination,
while normal fetches, headers, caching, errors, timeouts, and SSL context remain
covered.
The fix is present in the unreleased development branch. The patched version will be recorded after a released PyJWT 2.x version containing the fix is confirmed.
Credit
Credit: the original reporter of GHSA-9v7f-9g4p-ffgj. Additional redirect header-leak and cache-poisoning evidence from the newer duplicate report GHSA-43g3-98cx-x446 is preserved in the duplicate record and informed this canonical advisory update.
Maintainer update — 2026-09-11
The verified fix for this advisory is included in PyJWT 2.14.0, released on 2026-09-11 and available on PyPI. PyJWT 2.14.0 is the first release containing the fix. This advisory is now published with 2.14.0 recorded as the patched version.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pyjwt | all versions | 2.14.0pip install --upgrade 'pyjwt==2.14.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyjwt, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pyjwt to 2.14.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9v7f-9g4p-ffgj is resolved across your whole dependency graph.
Workarounds
Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.
Frequently Asked Questions
Is GHSA-9v7f-9g4p-ffgj in your dependencies?
Find it across PyPI, including transitive dependencies.