GHSA-jqcg-44mw-7w3h

Suggest an improvement
Source
https://github.com/advisories/GHSA-jqcg-44mw-7w3h
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-jqcg-44mw-7w3h/GHSA-jqcg-44mw-7w3h.json
JSON Data
https://api.test.osv.dev/v1/vulns/GHSA-jqcg-44mw-7w3h
Aliases
Published
2026-10-05T23:30:26Z
Modified
2026-10-05T23:45:09Z
Severity
  • 9.1 (Critical) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N CVSS Calculator
Summary
proxy-addr vulnerable to IP spoofing via IPv4-mapped IPv6 trust subnet
Details

Impact

proxy-addr determines which network hops are trusted proxies so that X-Forwarded-For can be believed. When an application configures a trust subnet as an IPv4-mapped IPv6 address with a short prefix, such as ::ffff:10.0.0.0/8 (the correct spelling is ::ffff:10.0.0.0/104), the subnet compiles with all-zero leading bits and matches every IPv4 address instead of the block it names. The same happens for any IPv6 trust subnet with zero leading bits, such as ::/1.

Every unauthenticated client is then trusted as a proxy at hop 0, so proxyaddr(req, trust), and therefore req.ip and req.ips in Express, returns whatever the client sends in X-Forwarded-For. This defeats IP-based access control, rate limiting, geolocation, and audit logging. The misconfiguration compiles without any error, and the same block written correctly behaves correctly, so the difference is not visible from the configuration.

Patches

Upgrade to proxy-addr 2.0.8. An IPv4 address now matches an IPv6 trust subnet only when that subnet is a genuine IPv4-mapped subnet whose prefix covers the mapped marker.

Workarounds

Write IPv4 trust subnets in plain IPv4 notation (for example 10.0.0.0/8). If IPv4-mapped IPv6 notation is required, use the full form so the prefix covers the mapped marker (for example ::ffff:10.0.0.0/104 for the 10.0.0.0/8 block).

Database specific 
{
    "cwe_ids": [
        "CWE-290",
        "CWE-348",
        "CWE-697"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-05T23:30:26Z",
    "nvd_published_at": "2026-09-15T07:16:33Z",
    "severity": "CRITICAL"
}
References

Affected packages

npm / proxy-addr

Package

Name
proxy-addr
View open source insights on deps.dev
Purl
pkg:npm/proxy-addr

Affected ranges

Type
SEMVER
Events
Introduced
1.1.0
Fixed
2.0.8

Database specific

source 
"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-jqcg-44mw-7w3h/GHSA-jqcg-44mw-7w3h.json"