EEF-CVE-2026-82756
- Source
- https://cna.erlef.org/osv/EEF-CVE-2026-82756.html
- Import Source
- https://cna.erlef.org/osv/EEF-CVE-2026-82756.json
- JSON Data
- https://api.osv.dev/v1/vulns/EEF-CVE-2026-82756
- Aliases
-
- GHSA-2h3v-83jg-2qmm
- CVE-2026-82756
- Published
- 2026-09-07T22:30:55.280Z
- Modified
- 2026-09-07T22:45:02.937213676Z
- Severity
-
- 6.3 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N CVSS Calculator
- Summary
- ash_authentication_oauth2_server interpolates a tenant-derived value into the WWW-Authenticate challenge without escaping, allowing header parameter injection
- Details
-
Summary
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.
Configuration
Reachable only in a multi-tenant application that derives the Ash tenant from request-controlled input (subdomain, Host, path, or header) and uses BearerPlug or RequireScopePlug; the tenant reaches the challenge through the server's tenant-aware resource_url.
- Database specific
{ "cwe_ids": [ "CWE-116" ], "capec_ids": [ "CAPEC-153" ], "cpe_ids": [ "cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*" ] }- References
-
- https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-2h3v-83jg-2qmm
- https://cna.erlef.org/cves/CVE-2026-82756.html
- https://github.com/ash-project/ash_authentication_oauth2_server/commit/09f97476715da031b136eaec7b2cda2363ad8149
- https://hex.pm/packages/ash_authentication_oauth2_server
- Credits
-
-
- Peter Ullrich - FINDER
-
- Peter Ullrich - REPORTER
-
- Zach Daniel / Ash Project - REMEDIATION_DEVELOPER
-
- Jonatan Männchen / EEF - COORDINATOR
-
Affected packages
Hex / ash_authentication_oauth2_server
Package
- Name
- ash_authentication_oauth2_server
- Purl
- pkg:hex/ash_authentication_oauth2_server