CVE-2026-49857: auth-fetch-mcp is an MCP server that lets AI assistants fetch content from authenticated web pages

Routine

HIGH 7.4

CVE-2026-49857 is a high-severity flaw (CVSS 7.4) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

auth-fetch-mcp is an MCP server that lets AI assistants fetch content from authenticated web pages. Version 3.0.1 implements SSRF protection in `assertSafeUrl()` (`src/security.ts`) to block requests to private and loopback addresses. However, the `isPrivateV6()` function fails to detect IPv4-mapped IPv6 loopback addresses in their hex-normalized form. When an attacker supplies a URL such as `http://[::ffff:127.0.0.1]:PORT/`, the Node.js WHATWG U

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.4 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.5% (top 59%)
CISA exploited list	No
Weakness	CWE-918
Published	2026-08-13
Last modified	2026-10-24

Publisher (CNA): GitHub, Inc.

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-08-13 15:19 UTCPublished CVE record published
2026-10-24 16:10 UTCUpdated Record last modified

Exact fixes by distribution

npm · auth-fetch-mcp · FIXED · 3.0.2 · vulnerable: <= 3.0.1 · source

npm install auth-fetch-mcp@">=3.0.2" npm ls auth-fetch-mcp

Fedora 46 · wasmedge · FIXED · 0.18.1-1.fc46 · FEDORA-2026-4c27216e39 · source

sudo dnf upgrade --advisory=FEDORA-2026-4c27216e39

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/ymw0407/auth-fetch-mcp/security/advisories/GHSA-pvrj-8cg3-j5f8

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-49857?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-49857 being exploited?

CVE-2026-49857 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-49857 affect?

CVE-2026-49857 affects affected software. Severity is high (CVSS 7.4). auth-fetch-mcp is an MCP server that lets AI assistants fetch content from authenticated web pages. Version 3.0.1 implements SSRF protection in `assertSafeUrl()` (`src/security.ts`) to block requests to private and loopback addresses. Howev

How urgent is CVE-2026-49857?

Priority 36/100. High severity

Software pages

Node.js vulnerabilities

References

← Back to latest CVEs