Improper Encoding or Escaping of Output vulnerability in ash-project ash_authentication_oauth2_server allows an unauthenticated attacker to inject arbitrary authentication parameters into the WWW-Authenticate challenge header.
BearerPlug and RequireScopePlug built the Bearer resource_metadata="..." challenge by interpolating a resource_metadata URL derived from the request tenant directly into the quoted value. In a multi-tenant application that sets the Ash tenant from request-controlled data (a subdomain, the Host, a path segment, or a header), a tenant containing a " closes the quoted value and appends attacker-chosen auth-params, including a second resource_metadata URL pointing at an attacker-controlled authorization server that spec-following clients follow. Carriage returns and line feeds are rejected by Plug, so this is parameter injection within one header, not response splitting.
This issue affects ash_authentication_oauth2_server: from 0.1.3 before 0.3.1.
BearerPlug and RequireScopePlug built the Bearer resource_metadata="..." challenge by interpolating a resource_metadata URL derived from the request tenant directly into the quoted value. In a multi-tenant application that sets the Ash tenant from request-controlled data (a subdomain, the Host, a path segment, or a header), a tenant containing a " closes the quoted value and appends attacker-chosen auth-params, including a second resource_metadata URL pointing at an attacker-controlled authorization server that spec-following clients follow. Carriage returns and line feeds are rejected by Plug, so this is parameter injection within one header, not response splitting.
This issue affects ash_authentication_oauth2_server: from 0.1.3 before 0.3.1.
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | ||||||
|---|---|---|---|---|---|---|---|---|---|
| ash-project | ash_authentication_oauth2_server | unaffected |
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| ash-project | ash_authentication_oauth2_server | unaffected |
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Mon, 07 Sep 2026 22:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | Improper Encoding or Escaping of Output vulnerability in ash-project ash_authentication_oauth2_server allows an unauthenticated attacker to inject arbitrary authentication parameters into the WWW-Authenticate challenge header. BearerPlug and RequireScopePlug built the Bearer resource_metadata="..." challenge by interpolating a resource_metadata URL derived from the request tenant directly into the quoted value. In a multi-tenant application that sets the Ash tenant from request-controlled data (a subdomain, the Host, a path segment, or a header), a tenant containing a " closes the quoted value and appends attacker-chosen auth-params, including a second resource_metadata URL pointing at an attacker-controlled authorization server that spec-following clients follow. Carriage returns and line feeds are rejected by Plug, so this is parameter injection within one header, not response splitting. This issue affects ash_authentication_oauth2_server: from 0.1.3 before 0.3.1. | |
| Title | ash_authentication_oauth2_server interpolates a tenant-derived value into the WWW-Authenticate challenge without escaping, allowing header parameter injection | |
| First Time appeared |
Ash-project
Ash-project ash Authentication Oauth2 Server |
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| Weaknesses | CWE-116 | |
| CPEs | cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Ash-project
Ash-project ash Authentication Oauth2 Server |
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| References |
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| Metrics |
cvssV4_0
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MITRE
Status: PUBLISHED
Assigner: EEF
Published:
Updated: 2026-09-07T22:30:55.280Z
Reserved: 2026-08-31T01:00:10.817Z
Link: CVE-2026-82756
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