CVE-2026-90711
CRITICAL · 9.1Real vuln + patch available, no KEV or PoC; early-stage vendor advisory amplification.
What: proxy-addr Node.js module (versions 1.1.0–2.0.7) misinterprets IPv4-mapped IPv6 CIDR notation, trusting all IPv4 addresses instead of intended subnets; CVSS 9.1 CRITICAL.
Why it matters: Regression defeats IP-based access control, rate limiting, geolocation, and audit logging via forged X-Forwarded-For headers. Fix available in 2.0.8. No KEV listing or public PoC reported yet, but advisory and patched release published same day; widely used in Express.js ecosystems.
Where it's seen: Aggregator alerts (stemshop, hackerwire, stackflag) and GitHub release notifications dominating chatter; no active exploitation chatter, mostly vendor advisory amplification.
RISK: HIGH — Regression in widely-deployed middleware; authentication bypass, but requires misconfigured CIDR subnet.
Description
proxy-addr is a Node.js module that determines a request's client address behind trusted reverse proxies, and it backs Express req.ip and req.ips. In versions 1.1.0 through 2.0.7, a trust subnet written in IPv4-mapped IPv6 notation with an IPv4-sized prefix, such as ::ffff:10.0.0.0/8 instead of the correct ::ffff:10.0.0.0/104, is accepted without error but trusts every IPv4 address on the internet rather than the block it names. Because the socket peer then becomes trusted at hop 0, any unauthenticated client can supply an arbitrary X-Forwarded-For header and control the address the application reads, which defeats IP-based access control, rate limiting, geolocation, and audit logging. This is a fail-open regression introduced in version 1.1.0. The issue is fixed in proxy-addr 2.0.8, and users should upgrade to 2.0.8 or later. As a workaround, ensure any IPv4-mapped IPv6 trust subnet uses a prefix length of at least 97, or express the range in plain IPv4 notation.
CVSS 3.1 breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N- Attack vector
- Network
- Complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None