CVE-2026-81315ash-project ash_ai
NVD
Vulnerability Summary
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.
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.
CVSS v4.0 Base Metrics — Score 7.4 (HIGH)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:NAttack VectorNetwork
Attack ComplexityLow
Attack RequirementsPresent
Privileges RequiredNone
User InteractionActive
Confidentiality (Vulnerable System)High
Integrity (Vulnerable System)High
Availability (Vulnerable System)None
Confidentiality (Subsequent System)None
Integrity (Subsequent System)None
Availability (Subsequent System)None
Affected & Patched Versions
- ash-project ash_ai >= 0.8.0 and < 1.0.0
- ash-project ash_ai >= c94f0b17fbe252f68755ba512678586164ba6139 and < 28af68d73134df0b8fb3aa6ab03e8fd795b07c21
- ash-project ash_ai 1.0.0
- ash-project ash_ai 28af68d73134df0b8fb3aa6ab03e8fd795b07c21
What to do
Fix it during your normal patch cycle. No exploitation is confirmed yet.
- Check whether you run ash-project ash_ai and which version.
- Update to a patched version listed above, then confirm the new version.
Timeline
- Aug 31, 2026Published
- Aug 31, 2026Record last modified
Score, severity and exploitation changes are tracked from the day Watchtower started logging them.
Get notified about new ash-project ash_ai CVEsYou are reading CVE-2026-81315. Get an email when KEV listings, exploits or new CVEs match your stack.
Set up CVE alertsMore ash-project ash_ai CVEs
External References
Data last checked: Nov 14, 2026 01:09 UTC