CVE-2026-81315

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Source
https://cve.org/CVERecord?id=CVE-2026-81315
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-81315.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-81315
Aliases
Published
2026-08-31T00:57:55.910Z
Modified
2026-09-01T03:46:14.079613865Z
Severity
  • 7.4 (High) CVSS_V4 - 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 CVSS Calculator
Summary
MCP DNS-rebinding origin check in AshAi is bypassed by a spoofed X-Forwarded-Proto header
Details

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 allowedorigins: nil, originallowed?/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.

Database specific 
{
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81315.json",
    "unresolved_ranges": [
        {
            "source": "AFFECTED_FIELD",
            "extracted_events": [
                {
                    "introduced": "c94f0b17fbe252f68755ba512678586164ba6139"
                },
                {
                    "fixed": "28af68d73134df0b8fb3aa6ab03e8fd795b07c21"
                }
            ]
        }
    ],
    "cna_assigner": "EEF",
    "cwe_ids": [
        "CWE-346"
    ]
}
References

Affected packages

Git / github.com/ash-project/ash_ai

Affected ranges

Type
GIT
Repo
https://github.com/ash-project/ash_ai
Events
Introduced
9dc782541629a80df5f13876b40c78ab882214a1
Fixed
f72b14744996e71df6d73480d617d963f340597b
Fixed
28af68d73134df0b8fb3aa6ab03e8fd795b07c21
Database specific
Show details 
{
    "source": [
        "DESCRIPTION",
        "REFERENCES"
    ],
    "extracted_events": [
        {
            "introduced": "0.8.0"
        },
        {
            "fixed": "1.0.0"
        }
    ]
}

Affected versions

v0.*
v0.8.0
v0.8.1
v0.8.2

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-81315.json"