# Backstage catalog rules can be bypassed for URL locations using encoded path segments

Advisory record · `GHSA-w658-mh9p-ww8f`

- **Identifiers:** `GHSA-w658-mh9p-ww8f` · `CVE-2026-115923`
- **State:** Confirmed
- **Severity:** CVSS 6.5 Medium
- **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:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 28 Oct 2026, 22:42 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `@backstage/plugin-catalog-backend` (npm): affected `<3.9.2 || >=4.0.0, <4.0.2`; fixed in `3.9.2`, `4.0.2`

## 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

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

- **CISA KEV:** Not listed.
- **EPSS:** 0.0032, the 24th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 26 Oct 2026, 17:56 UTC: [Confirmed by the CVE List](https://www.cve.org/CVERecord?id=CVE-2026-115923)
- 26 Oct 2026, 18:17 UTC: [Confirmed by NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-115923)
- 31 Oct 2026, 13:32 UTC: First seen by agentprime
- 31 Oct 2026, 13:32 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-w658-mh9p-ww8f)

## Sources

- [GitHub Advisory Database: GHSA-w658-mh9p-ww8f](https://github.com/advisories/GHSA-w658-mh9p-ww8f)
- [OSV: GHSA-w658-mh9p-ww8f](https://osv.dev/vulnerability/GHSA-w658-mh9p-ww8f)
- <https://github.com/backstage/backstage/security/advisories/GHSA-w658-mh9p-ww8f>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-115923>
- <https://github.com/backstage/backstage/commit/3214dc8f15d4a08a2fd07a72a8fe4d00aeac0db4>
- <https://github.com/backstage/backstage/commit/737ff1c719dbd5a97f375b7f1db6d61416618419>
- <https://github.com/backstage/backstage>
- <https://github.com/backstage/backstage/releases/tag/v1.54.10>
- <https://github.com/backstage/backstage/releases/tag/v1.56.1>

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-w658-mh9p-ww8f>, 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-w658-mh9p-ww8f/>. Everything for agents: <https://agentprime.io/llms.txt>.