ash-project ash_ai up to 0.9.x Origin Validation AshAi.Mcp.Server.origin_allowed dns rebinding

Summaryinfo

A vulnerability marked as critical has been reported in ash-project ash_ai up to 0.9.x. The affected element is the function AshAi.Mcp.Server.origin_allowed of the component Origin Validation. The manipulation leads to dns rebinding. This vulnerability is referenced as CVE-2026-81315. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability was found in ash-project ash_ai up to 0.9.x. It has been rated as critical. This issue affects the function AshAi.Mcp.Server.origin_allowed of the component Origin Validation. The manipulation with an unknown input leads to a dns rebinding vulnerability. Using CWE to declare the problem leads to CWE-350. The product performs reverse DNS resolution on an IP address to obtain the hostname and make a security decision, but it does not properly ensure that the IP address is truly associated with the hostname. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Origin Validation Error vulnerability in ash-project ash_ai allows a malicious web page to bypass the MCP server's DNS-rebinding protection and issue cross-site requests to a user's local MCP server with that user's actor. In AshAi.Mcp.Server, with the default allowed_origins: nil, origin_allowed?/3 accepts an origin when uri.host == conn.host and the forwarded scheme is https. Both values are attacker-controlled: conn.host comes from the Host header and the scheme is read from the raw x-forwarded-proto header with no trusted-proxy check. Under DNS rebinding the browser sends the attacker's origin and a matching host, and page JavaScript may set X-Forwarded-Proto: https, so the check passes with no TLS or proxy involved. The fix trusts only localhost origins by default; other origins require an explicit allowed_origins allowlist. This issue affects ash_ai: from 0.8.0 before 1.0.0.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-81315 since 08/30/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/31/2026). MITRE ATT&CK project uses the attack technique T1583.002 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Project Management Software

Vendor

• ash-project

Name

• ash_ai

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9

Website

• Product: https://github.com/ash-project/ash_ai/

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