CVE-2026-82754 Details
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.
A vulnerability in the ash-project's ash_authentication_oauth2_server package, specifically in versions 0.1.0 prior to 0.3.1, allows state-changing OAuth endpoints to be accessed under an unintended URL prefix. This issue bypasses controls that are normally applied to the canonical prefix. The vulnerability arises because the same ProtocolRouter is forwarded at both the /oauth and /.well-known prefixes. Since Phoenix strips the matched prefix before dispatching, the full route table is accessible under both mounts. As a result, POST requests to /register, /token, and /revoke can be made through the /.well-known/register, /.well-known/token, and /.well-known/revoke endpoints. This exploitation can bypass edge controls such as WAF rules, rate limits, or authentication exemptions that are scoped to the /oauth paths or allow-list the /.well-known prefix as unauthenticated.
Users can upgrade to ash_authentication_oauth2_server version 0.3.1 or later, where this vulnerability has been fixed. Alternatively, edge controls can be applied to both the /oauth and /.well-known prefixes, or the protocol routes can be mounted under a single prefix to avoid the issue.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 7, 2026CISA-ADP
Assessed Sep 8, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://cna.erlef.org/cves/CVE-2026-82754.html | EEF | Advisory |
| https://github.com/ash-project/ash_authentication_oauth2_server/commit/a72972d7ed3eb74c05dfa0653a258ef14454459a | EEF | Source CodeVendor |
| https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-wwxg-h779-3wf4 | EEF | AdvisoryRemedyVendor |
| https://osv.dev/vulnerability/EEF-CVE-2026-82754 | EEF | AdvisoryVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-424 | Improper Protection of Alternate Path | EEF |
Affected Products
| Product | Versions |
|---|---|
| ash_authentication_oauth2_server | >= 0.1.0, < 0.3.1 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 8, 2026 | CVE Modified | CISA-ADP |
| Sep 7, 2026 | New CVE Received | EEF |