Path Traversal in Backstage
CVE-2026-115923
Backstage is an open framework for building developer portals. Prior to 3.9.2 and from 4.0.0 until 4.0.2, DefaultCatalogRulesEnforcer in @backstage/plugin-catalog-backend compares the raw location.target URL against catalog.rules, while URL readers canonicalize the same URL before fetching it. An authenticated user with catalog.location.create permission can use percent-encoded path segments to make an untrusted URL match a trusted location pattern even though the canonical URL resolves outside that scope. This admits entity content from an untrusted source as trusted, while further downstream consequences depend on deployment configuration. This issue is fixed in versions 3.9.2 and 4.0.2.
Vulnerability class: Path Traversal (Directory Traversal)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Backstage — versions < 3.9.2, >= 4.0.0, < 4.0.2
Weakness classification (CWE)
References
- github.com/backstage/backstage/security/advisories/GHSA-w658-mh9p-ww8f
- github.com/backstage/backstage/commit/3214dc8f15d4a08a2fd07a72a8fe4d00aeac0db4
- github.com/backstage/backstage/commit/737ff1c719dbd5a97f375b7f1db6d61416618419
- github.com/backstage/backstage/releases/tag/v1.54.10
- github.com/backstage/backstage/releases/tag/v1.56.1
Frequently asked questions
- What is CVE-2026-115923?
- CVE-2026-115923 is a medium-severity vulnerability in Backstage, classified under Path Traversal. CVSS score: 6.5/10. Published 2026-10-26.
- How severe is CVE-2026-115923?
- Medium severity. CVSS v3 base score is 6.5 out of 10.