CVE-2026-82754
ash_authentication_oauth2_server aliases every protocol endpoint under /.well-known, bypassing path-scoped controls
- State
- Published
- Severity
- 6.3 Medium
- Published
- Sep 7, 2026
- Updated
- Sep 8, 2026
- Reserved
- Aug 31, 2026
Description
Improper Protection of Alternate Path vulnerability in ash-project ash_authentication_oauth2_server exposes the state-changing OAuth endpoints under an unintended URL prefix, bypassing controls scoped to the canonical prefix.
oauth2_server_protocol_routes/1 in AshAuthentication.Phoenix.Oauth2Server.Router forwards the same ProtocolRouter at both the /oauth prefix and the /.well-known prefix. Phoenix forward strips the matched prefix before dispatch, so the full route table answers under both mounts, and POST /register, POST /token, and POST /revoke are reachable as /.well-known/register, /.well-known/token, and /.well-known/revoke. Edge controls such as WAF rules, rate limits, or authentication exemptions written against the /oauth paths, or that allow-list /.well-known as unauthenticated, do not apply to the alias.
This issue affects ash_authentication_oauth2_server: from 0.1.0 before 0.3.1.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 6.3 Medium | 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 | EEF |
Weaknesses
- CWE-424 Improper Protection of Alternate Path
Affected Products
| Product | Versions |
|---|---|
ash_authentication_oauth2_serverash-project |
|
ash_authentication_oauth2_serverash-project |
|
References
- https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-wwxg-h779-3wf4vendor-advisoryrelated
- https://cna.erlef.org/cves/CVE-2026-82754.htmlrelated
- https://osv.dev/vulnerability/EEF-CVE-2026-82754related
- https://github.com/ash-project/ash_authentication_oauth2_server/commit/a72972d7ed3eb74c05dfa0653a258ef14454459apatch
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