CVE-2026-82756: CWE-116 Improper Encoding or Escaping of Output in ash-project ash_authentication_oauth2_server
CVE-2026-82756 is a medium severity vulnerability in ash-project's ash_authentication_oauth2_server affecting versions 0.1.3 up to but not including 0.3.1. It involves improper encoding or escaping of output, allowing an unauthenticated attacker to inject arbitrary authentication parameters into the WWW-Authenticate challenge header. This occurs because certain plugs interpolate tenant-derived URLs directly into quoted header values without proper escaping, enabling parameter injection within a single header.
AI Analysis
Technical Summary
The vulnerability in ash_authentication_oauth2_server arises from improper encoding or escaping of output in the construction of the WWW-Authenticate challenge header. Specifically, BearerPlug and RequireScopePlug interpolate a resource_metadata URL derived from the request tenant directly into a quoted header value. In multi-tenant setups where the tenant is set from request-controlled data, an attacker can craft a tenant value containing a quote character to break out of the quoted string and inject additional authentication parameters, including a malicious resource_metadata URL. Carriage returns and line feeds are rejected, so this is parameter injection within a single header rather than response splitting. This affects versions from 0.1.3 before 0.3.1.
Potential Impact
An unauthenticated attacker can inject arbitrary authentication parameters into the WWW-Authenticate challenge header, potentially causing clients to follow attacker-controlled authorization servers. This could lead to authentication bypass or redirection to malicious authorization endpoints in multi-tenant applications using vulnerable versions of ash_authentication_oauth2_server.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch is currently documented. Until a fix is available, avoid setting tenant values from untrusted request data or implement strict validation and escaping of tenant-derived values used in headers to prevent injection.
CVE-2026-82756: CWE-116 Improper Encoding or Escaping of Output in ash-project ash_authentication_oauth2_server
Description
CVE-2026-82756 is a medium severity vulnerability in ash-project's ash_authentication_oauth2_server affecting versions 0.1.3 up to but not including 0.3.1. It involves improper encoding or escaping of output, allowing an unauthenticated attacker to inject arbitrary authentication parameters into the WWW-Authenticate challenge header. This occurs because certain plugs interpolate tenant-derived URLs directly into quoted header values without proper escaping, enabling parameter injection within a single header.
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 in ash_authentication_oauth2_server arises from improper encoding or escaping of output in the construction of the WWW-Authenticate challenge header. Specifically, BearerPlug and RequireScopePlug interpolate a resource_metadata URL derived from the request tenant directly into a quoted header value. In multi-tenant setups where the tenant is set from request-controlled data, an attacker can craft a tenant value containing a quote character to break out of the quoted string and inject additional authentication parameters, including a malicious resource_metadata URL. Carriage returns and line feeds are rejected, so this is parameter injection within a single header rather than response splitting. This affects versions from 0.1.3 before 0.3.1.
Potential Impact
An unauthenticated attacker can inject arbitrary authentication parameters into the WWW-Authenticate challenge header, potentially causing clients to follow attacker-controlled authorization servers. This could lead to authentication bypass or redirection to malicious authorization endpoints in multi-tenant applications using vulnerable versions of ash_authentication_oauth2_server.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch is currently documented. Until a fix is available, avoid setting tenant values from untrusted request data or implement strict validation and escaping of tenant-derived values used in headers to prevent injection.
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: 6a9f4039acd9273b4972ed9b
Added to database: 09/07/2026, 22:52:41 UTC
Last enriched: 09/07/2026, 23:08:01 UTC
Last updated: 09/08/2026, 01:16:45 UTC
Views: 6
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