{"cve":"CVE-2026-81315","nvd":{"published":"2026-08-31T01:16:49.977","modified":"2026-09-01T21:15:00.147","status":"Deferred","description":"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.\n\nIn 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.\n\nThis issue affects ash_ai: from 0.8.0 before 1.0.0.","cvss_v4":{"vector":"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","score":7.4},"cvss_v3":null,"cwes":["CWE-346"],"references":["https://cna.erlef.org/cves/CVE-2026-81315.html","https://github.com/ash-project/ash_ai/commit/28af68d73134df0b8fb3aa6ab03e8fd795b07c21","https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49h","https://osv.dev/vulnerability/EEF-CVE-2026-81315","https://github.com/ash-project/ash_ai/security/advisories/GHSA-c92r-f3rr-q49h"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:50.842544443+00:00"},"epss":{"cve":"CVE-2026-81315","score":0.00278,"percentile":0.20243,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}