Medium 6.5Published Oct 26, 2026

CVE-2026-115923Backstage catalog rules can be bypassed for URL locations using encoded path segments

Updated under an hour ago (Oct 28, 2026, 9:10 PM ET)

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No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

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.

CVSS: 6.5 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Weakness (CWE): CWE-22
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Awaiting Analysis
Record last updated: Oct 26, 2026
First seen by InfoSec Signals: Oct 26, 2026

Affected products

Affected products

backstage backstage backstage:backstage (from the name)	before 3.9.2; from 4.0.0, < 4.0.2	CNA record

References

References

https://github.com/backstage/backstage/security/advisories/GHSA-w658-mh9p-ww8f	x-refsource-confirm
https://github.com/backstage/backstage/commit/3214dc8f15d4a08a2fd07a72a8fe4d00aeac0db4	x-refsource-misc
https://github.com/backstage/backstage/commit/737ff1c719dbd5a97f375b7f1db6d61416618419	x-refsource-misc
https://github.com/backstage/backstage/releases/tag/v1.54.10	x-refsource-misc
https://github.com/backstage/backstage/releases/tag/v1.56.1	x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.