CVE-2026-82754: CWE-424 Improper Protection of Alternate Path in ash-project ash_authentication_oauth2_server
CVE-2026-82754 is an improper protection of alternate path vulnerability in ash-project's ash_authentication_oauth2_server. The OAuth2 server routes are accessible under both the intended /oauth prefix and an unintended /.well-known prefix, allowing state-changing endpoints to bypass controls scoped only to the canonical /oauth path. This affects versions from 0.1.0 up to but not including 0.3.1.
AI Analysis
Technical Summary
The vulnerability arises because the AshAuthentication.Phoenix.Oauth2Server.Router forwards the same ProtocolRouter at both /oauth and /.well-known prefixes. Due to Phoenix framework behavior, the matched prefix is stripped before dispatch, causing the full route table to be accessible under both prefixes. Consequently, POST endpoints such as /register, /token, and /revoke are reachable via /.well-known/register, /.well-known/token, and /.well-known/revoke. This allows bypassing edge controls like WAF rules, rate limits, or authentication exemptions that are applied only to the /oauth prefix or treat /.well-known as unauthenticated. The affected versions are ash_authentication_oauth2_server 0.1.0 through versions before 0.3.1.
Potential Impact
Attackers can access state-changing OAuth endpoints through an alternate URL prefix that bypasses security controls scoped to the canonical /oauth prefix. This could lead to unauthorized token registration, issuance, or revocation actions if protections rely solely on the /oauth path. The vulnerability has a CVSS 4.0 score of 6.3 (medium severity), indicating a moderate risk without requiring privileges or user interaction.
Mitigation Recommendations
No official patch or remediation level is currently documented. Users should monitor the vendor advisory for updates. Until a fix is available, security controls such as WAF rules, rate limits, and authentication exemptions should be applied to both the /oauth and /.well-known prefixes to prevent bypass. Avoid allowing unauthenticated access to /.well-known paths that map to sensitive OAuth endpoints.
CVE-2026-82754: CWE-424 Improper Protection of Alternate Path in ash-project ash_authentication_oauth2_server
Description
CVE-2026-82754 is an improper protection of alternate path vulnerability in ash-project's ash_authentication_oauth2_server. The OAuth2 server routes are accessible under both the intended /oauth prefix and an unintended /.well-known prefix, allowing state-changing endpoints to bypass controls scoped only to the canonical /oauth path. This affects versions from 0.1.0 up to but not including 0.3.1.
CVSS v4.0
Score 6.3medium
Affected software
pkg:hex/ash_authentication_oauth2_serverpkg:github/ash-project/ash_authentication_oauth2_servercpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability arises because the AshAuthentication.Phoenix.Oauth2Server.Router forwards the same ProtocolRouter at both /oauth and /.well-known prefixes. Due to Phoenix framework behavior, the matched prefix is stripped before dispatch, causing the full route table to be accessible under both prefixes. Consequently, POST endpoints such as /register, /token, and /revoke are reachable via /.well-known/register, /.well-known/token, and /.well-known/revoke. This allows bypassing edge controls like WAF rules, rate limits, or authentication exemptions that are applied only to the /oauth prefix or treat /.well-known as unauthenticated. The affected versions are ash_authentication_oauth2_server 0.1.0 through versions before 0.3.1.
Potential Impact
Attackers can access state-changing OAuth endpoints through an alternate URL prefix that bypasses security controls scoped to the canonical /oauth prefix. This could lead to unauthorized token registration, issuance, or revocation actions if protections rely solely on the /oauth path. The vulnerability has a CVSS 4.0 score of 6.3 (medium severity), indicating a moderate risk without requiring privileges or user interaction.
Mitigation Recommendations
No official patch or remediation level is currently documented. Users should monitor the vendor advisory for updates. Until a fix is available, security controls such as WAF rules, rate limits, and authentication exemptions should be applied to both the /oauth and /.well-known prefixes to prevent bypass. Avoid allowing unauthenticated access to /.well-known paths that map to sensitive OAuth endpoints.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- EEF
- Date Reserved
- 2026-08-31T01:00:10.817Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a9f3cc3acd9273b496d74c1
Added to database: 09/07/2026, 22:37:55 UTC
Last enriched: 09/07/2026, 22:52:58 UTC
Last updated: 09/08/2026, 00:16:37 UTC
Views: 4
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