CVE-2026-82756

Published Sep 7, 2026 Modified Sep 8, 2026 CWE-116

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.

Is your site exposed to CVE-2026-82756?

Run a free security scan — no signup, results in seconds.

EPSS — Exploit Prediction

0.0038
Probability of exploitation
0.31%
Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-116 CWE-116

References

Frequently Asked Questions

What is CVE-2026-82756? +
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.
How do I check if I'm vulnerable to CVE-2026-82756? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-88060

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.30, …
CVE-2026-62681

Orval generates type-safe JavaScript clients in TypeScript from OpenAPI v3 and Swagger v2 specifications. Prior to 8.21.0, an unescaped backtick …
CVE-2026-71864

Orval generates type-safe JavaScript clients in TypeScript from OpenAPI v3 and Swagger v2 specifications. Prior to 8.21.0, a double quote …
CVE-2026-50642

diff‑so‑fancy does not properly sanitize non‑SGR terminal control sequences before outputting diff data. The application only strips ANSI SGR sequences …
CVE-2026-88058

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.30, …
CVE-2026-83610

xmldom is a pure JavaScript W3C standard-based (XML DOM Level 2 Core) DOMParser and XMLSerializer module. Prior to @xmldom/xmldom versions …

Don't wait for an exploit

Scan your website for vulnerabilities like CVE-2026-82756 — free, no signup required.