CVE-2026-41425 — authlib
MEDIUMCVE-2026-41425 is a medium-severity (CVSS 5.4) Cross-Site Request Forgery (CSRF) vulnerability in authlib. A fix is available for authlib — see the affected versions and patch details below.
Authlib: Cross-site request forging when using cache
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-41425.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
authlibReal-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
There is no CSRF protection on the cache feature on most integrations clients.
Details
In authlib.integrations.starlette_client.OAuth, no CSRF protection is set up when using the cache parameter. When not using the cache parameter, the use of SessionMiddleware ties the client to the auth state, preventing CSRF attacks. With the cache, there is no such mechanism. Other integratons have the same issue, it's not just starlette.
The state parameter is taken from the callback URL and the state is fetched from the cache without checking that it is the same client calling the redirect endpoint as was the one that initiated the auth flow.
This issue is documented in RFC 6749 section 10.12: https://datatracker.ietf.org/doc/html/rfc6749#section-10.12
PoC
- Set up a Starlette integration with a cache
- The attacker starts the auth flow up until before the callback URL is followed.
- The attacked sends the redirect URL to the victim
- The victim now completes the authorisation
Impact
This impacts all users that use the cache to store auth state.
All users will be vulnerable to CSRF attacks and may have an attacker's account tied to their own.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | authlib | all versions | 1.6.11pip install --upgrade 'authlib==1.6.11' |
Affected Products
authlibauthlibDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for authlib, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update authlib to 1.6.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-41425 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
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.Source: Red Hat security advisory for CVE-2026-41425 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-41425 in your dependencies?
Find it across PyPI, including transitive dependencies.