# CVE-2026-82758

## Summary

- **CVE ID:** CVE-2026-82758
- **Severity:** MEDIUM
- **CVSS Score:** 6.3 (CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N)
- **CWE:** CWE-287
- **Published:** Sep 7, 2026
- **Last Modified:** Sep 8, 2026

## Description

Improper Authentication vulnerability in ash-project ash_authentication_oauth2_server allows an unauthenticated attacker to register OAuth clients even when Dynamic Client Registration is gated by an initial access token.

resolve_secret/3 in AshAuthentication.Oauth2Server (reached through __resolve_secret__!) treated any return other than {:ok, _} or :error from a configured {module, function, args} or 2-arity-function secret provider as a valid secret, wrapping nil, false, or "" as {:ok, value}. When the initial_access_token resolves to such an empty value, POST /oauth/register compares the presented bearer token against it and the comparison passes with no token supplied, so registration is open although it was configured closed. The same fail-open affected other resolved secrets such as signing_secret.

This issue affects ash_authentication_oauth2_server: from 0.1.0 before 0.3.1.

## Affected Products

- ash-project — ash_authentication_oauth2_server (0.1.0)
- ash-project — ash_authentication_oauth2_server (855b578037c5ded18e8a6e60f42e56bde4905fae)

## References

- [CNA](https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-fxc6-vp68-87pw)
- [CNA](https://cna.erlef.org/cves/CVE-2026-82758.html)
- [CNA](https://osv.dev/vulnerability/EEF-CVE-2026-82758)
- [CNA](https://github.com/ash-project/ash_authentication_oauth2_server/commit/30a87101871775d27d79f9ad6f29eafa4779e118)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.38%
- **EPSS Percentile:** 31.4

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-09._