# CVE-2026-82756: ash-project ash_authentication_oauth2_server parameter injection in WWW-Authenticate header

Source: https://junglewise.ai/threats/cve-2026-82756-ash-project-ash-authentication-oauth2-server-parameter-injection  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-07. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-82756 · Severity: info · Published 2026-09-07

The ash_authentication_oauth2_server library is used to handle OAuth2 authentication in multi-tenant applications. An attacker can inject malicious authentication parameters into the WWW-Authenticate response header by crafting a tenant name containing special characters, potentially redirecting authentication requests to an attacker-controlled authorization server and compromising user login flows.

Technologies: [Ash-Project Ash Authentication Oauth2 Server](https://junglewise.ai/threats/technologies/ash-authentication-oauth2-server). Vendors: [Ash-Project](https://junglewise.ai/threats/vendors/ash-project).

## Quick answers

**Is CVE-2026-82756 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-82756 being exploited in the wild.

**How severe is CVE-2026-82756?** Informational severity, published 7 September 2026.

**Which products and versions are affected?** Ash-Project Ash Authentication Oauth2 Server 0.1.3 to 0.3.0.

**Is there a fix for CVE-2026-82756?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-82756 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-82756?** Check whether you run Ash-Project Ash Authentication Oauth2 Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

This is an improper encoding/escaping vulnerability in the BearerPlug and RequireScopePlug components. The vulnerability occurs when the library constructs a Bearer resource_metadata challenge by directly interpolating a resource_metadata URL derived from the tenant identifier into a quoted header value without proper escaping. In multi-tenant applications where the tenant is derived from request-controlled data (subdomain, Host header, path segment), an attacker can include a double-quote character in the tenant name to close the quoted value and inject additional authentication parameters. The injected parameters can include a malicious resource_metadata URL pointing to an attacker-controlled authorization server. While Plug rejects carriage returns and line feeds, preventing response splitting, parameter injection within the single header remains possible. Affected versions are 0.1.3 through 0.3.0; version 0.3.1 and later contain the fix. No authentication is required; only network access to the vulnerable application is needed.

## Affected products

- ash-project ash_authentication_oauth2_server 0.1.3 to 0.3.0

## Timeline

- 2026-09-07: disclosed

## References

- [https://repo.hex.pm/](https://repo.hex.pm/)
- [https://github.com/](https://github.com/)

## Related threats

- [ash-project ash_authentication_oauth2_server authentication bypass in client registration](https://junglewise.ai/threats/cve-2026-82758-ash-project-ash-authentication-oauth2-server-authentication)
- [ash-project ash_authentication_oauth2_server SSRF in metadata fetch](https://junglewise.ai/threats/cve-2026-82757-ash-project-ash-authentication-oauth2-server-ssrf-in-metadata)
- [ash-project ash_authentication_oauth2_server cache poisoning in OAuth discovery metadata](https://junglewise.ai/threats/cve-2026-82755-ash-project-ash-authentication-oauth2-server-cache-poisoning-in)
- [ash-project ash_authentication_oauth2_server path traversal in OAuth endpoints](https://junglewise.ai/threats/cve-2026-82754-ash-project-ash-authentication-oauth2-server-path-traversal-in)
- [ash-project ash_authentication_oauth2_server unbound resource allocation in /authorize](https://junglewise.ai/threats/cve-2026-82753-ash-project-ash-authentication-oauth2-server-unbound-resource)