# Fiber unauthorized access vulnerability in \`ctx.IsFromLocal()\`

Advisory record · `GHSA-3q5p-3558-364f`

- **Identifiers:** `GHSA-3q5p-3558-364f` · `CVE-2023-41338` · `GO-2023-2052`
- **State:** Confirmed
- **Severity:** CVSS 5.3 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-670](https://cwe.mitre.org/data/definitions/670.html)
- **Tags:** [CWE-670](https://agentprime.io/advisories/tag/cwe-670.md)
- **Published:** 8 Sept 2023
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 8 Sept 2023, 13:27 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/gofiber/fiber` (Go): affected `<=1.14.6`; no fixed version yet
- `github.com/gofiber/fiber/v2` (Go): affected `<2.49.2`; fixed in `2.49.2`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Fiber's ctx.IsFromLocal() method in github.com/gofiber/fiber/v2 versions before 2.49.2 can be fooled into returning true for remote clients, because it relies on the X-Forwarded-For header. A remote attacker who sends that header with a localhost address can reach resources meant only for local access. Upgrade github.com/gofiber/fiber/v2 to 2.49.2 or later. The github.com/gofiber/fiber package (versions up to 1.14.6) is also listed as affected with no fixed version.

Written 2 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 5.3 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0066, the 51st percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:15 UTC: First seen by agentprime
- 31 Oct 2026, 14:15 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-3q5p-3558-364f)

## Sources

- [GitHub Advisory Database: GHSA-3q5p-3558-364f](https://github.com/advisories/GHSA-3q5p-3558-364f)
- [OSV: GHSA-3q5p-3558-364f](https://osv.dev/vulnerability/GHSA-3q5p-3558-364f)
- <https://github.com/gofiber/fiber/security/advisories/GHSA-3q5p-3558-364f>
- <https://nvd.nist.gov/vuln/detail/CVE-2023-41338>
- <https://github.com/gofiber/fiber/commit/b8c9ede6efa231116c4bd8bb9d5e03eac1cb76dc>
- <https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-For>
- <https://docs.gofiber.io/api/ctx#isfromlocal>
- <https://github.com/gofiber/fiber>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-3q5p-3558-364f>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-3q5p-3558-364f/>. Everything for agents: <https://agentprime.io/llms.txt>.