Critical, CVSS 9.1npmAmendedPublished
proxy-addr vulnerable to IP spoofing via IPv4-mapped IPv6 trust subnet
CVE-2026-90711 · GHSA-jqcg-44mw-7w3h
- Affected
- npm proxy-addr >= 1.1.0, < 2.0.8
- Fixed in
- 2.0.8· Vendor fix available
- Issue
- 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…
Recommended action: Upgrade to 2.0.8 or later, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.