CVE-2026-28802 — authlib
Fix: authlib/authlib@a61c2acCVE-2026-28802 is a CWE-347 vulnerability in authlib. A fix is available for authlib — see the affected versions and patch details below.
Authlib: Setting `alg: none` and a blank signature appears to bypass signature verification
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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 CVE-2026-28802.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
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
Authlib is a Python library which builds OAuth and OpenID Connect servers. From version 1.6.5 to before version 1.6.7, previous tests involving passing a malicious JWT containing alg: none and an empty signature was passing the signature verification step without any changes to the application code when a failure was expected.. This issue has been patched in version 1.6.7.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | authlib | ≥ 1.6.5&&< 1.6.7 | 1.6.7pip install --upgrade 'authlib==1.6.7' |
Detection & 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 1.6.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-28802 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-28802 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-28802. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
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.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Ansible Automation Platform 2.6 | ansible-automation-platform-26/lightspeed-chatbot-rhel9:1774417022 | RHSA-2026:6309 |
| Red Hat Ansible Automation Platform 2.6 | ansible-automation-platform-26/lightspeed-chatbot-rhel9:1774417022 | RHSA-2026:6404 |
| Red Hat Quay 3.10 | quay/quay-rhel8:1773971077 | RHSA-2026:5665 |
| Red Hat Quay 3.12 | quay/quay-rhel8:1773771962 | RHSA-2026:4942 |
| Red Hat Quay 3.15 | quay/quay-rhel8:1775169219 | RHSA-2026:6568 |
| Red Hat Quay 3.16 | quay/quay-rhel9:1779204086 | RHSA-2026:19375 |
| Red Hat Quay 3.9 | quay/quay-rhel8:1773936323 | RHSA-2026:5168 |
Frequently Asked Questions
Is CVE-2026-28802 in your dependencies?
O3 Security finds CVE-2026-28802 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.