High 7.4Published Aug 31, 2026

CVE-2026-81315MCP DNS-rebinding origin check in AshAi is bypassed by a spoofed X-Forwarded-Proto header

Updated under an hour ago (2026-10-19 10:00 UTC)

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It affects ash-project ash_ai. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for ash-project ash_ai

Exploited in the last 30 days

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.

CVSS: 7.4 HIGH (v4.0, CNA)CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Weakness (CWE): CWE-346
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: EEF
NVD analysis: Deferred
Record last updated: Aug 31, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

ash-project ash_ai ash-project:ash_ai	from 0.8.0 before 1.0.0	CNA record

References

https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49hvendor-advisory, related
https://cna.erlef.org/cves/CVE-2026-81315.htmlrelated
https://osv.dev/vulnerability/EEF-CVE-2026-81315related
https://github.com/ash-project/ash_ai/commit/28af68d73134df0b8fb3aa6ab03e8fd795b07c21patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.