# Echo: Encoded slash (%2F) bypasses route-level protection and exposes static files

Advisory record · `GHSA-vfp3-v2gw-7wfq`

- **Identifiers:** `GHSA-vfp3-v2gw-7wfq` · `CVE-2026-55677` · `GO-2026-6293`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-22](https://cwe.mitre.org/data/definitions/22.html)
- **Tags:** [Path traversal](https://agentprime.io/advisories/tag/path-traversal.md)
- **Published:** 25 Aug 2026
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 25 Aug 2026, 16:13 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/labstack/echo/v5` (Go): affected `<5.2.0`; fixed in `5.2.0`
- `github.com/labstack/echo/v4` (Go): affected `<4.15.3`; fixed in `4.15.3`
- `github.com/labstack/echo` (Go): affected `<=3.3.10`; no fixed version yet

## 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

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

- **CISA KEV:** Not listed.
- **EPSS:** 0.0052, the 44th percentile, on 13 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 14 Jun 2026, 15:08 UTC: [Published by the maintainers as a GitHub repository advisory](https://github.com/labstack/echo/security/advisories/GHSA-vfp3-v2gw-7wfq)
- 31 Oct 2026, 14:13 UTC: First seen by agentprime
- 31 Oct 2026, 14:13 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-vfp3-v2gw-7wfq)

## Sources

- [GitHub Advisory Database: GHSA-vfp3-v2gw-7wfq](https://github.com/advisories/GHSA-vfp3-v2gw-7wfq)
- [OSV: GHSA-vfp3-v2gw-7wfq](https://osv.dev/vulnerability/GHSA-vfp3-v2gw-7wfq)
- <https://github.com/labstack/echo/security/advisories/GHSA-vfp3-v2gw-7wfq>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-55677>
- <https://github.com/labstack/echo/pull/3009>
- <https://github.com/labstack/echo/pull/3011>
- <https://github.com/labstack/echo/commit/8d1ae9d3360a71672418856d58753af25f2c3986>
- <https://github.com/labstack/echo/commit/c3fa2a27ff92b2b8db360de614f999ef1da24725>
- <https://github.com/labstack/echo>
- <https://github.com/labstack/echo/releases/tag/v4.15.3>
- <https://github.com/labstack/echo/releases/tag/v5.2.0>

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-vfp3-v2gw-7wfq>, 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-vfp3-v2gw-7wfq/>. Everything for agents: <https://agentprime.io/llms.txt>.