CVE-2026-115923
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Path Traversal in Backstage Plugin Catalog Backend

Publication date: 2026-10-26

Last updated on: 2026-10-26

Assigner: GitHub, Inc.

Description
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.

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Meta Information

Published
2026-10-26
Last Modified
2026-10-26
Generated
2026-10-26
AI Q&A
2026-10-26
EPSS Evaluated
N/A
NVD
CVE-2026-115923
EUVD
EUVD-2026-110054

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
backstage backstage < 3.9.2
backstage backstage >= 4.0.0, < 4.0.2

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-22 The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

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Executive Summary

CVE-2026-115923 is a vulnerability in Backstage's plugin-catalog-backend where URL locations in catalog rules are matched against raw URLs instead of canonicalized versions. This allows attackers to bypass security checks by using percent-encoded path segments, making an untrusted URL appear trusted during rule evaluation while resolving to a different location when fetched.

Detection Guidance

To detect this vulnerability, check the installed version of the @backstage/plugin-catalog-backend package. If it is between 4.0.0 and 4.0.2 or below 3.9.2, the system is vulnerable. Run: npm list @backstage/plugin-catalog-backend or yarn list @backstage/plugin-catalog-backend to verify the version.

Impact Analysis

An authenticated user with catalog.location.create permissions can register entities from untrusted sources as trusted. This may lead to unintended actions by processors or scaffolder tools based on ingested entity content, potentially causing data breaches or unauthorized system modifications.

Mitigation Strategies

Upgrade the @backstage/plugin-catalog-backend package to version 3.9.2 or 4.0.2 or later. If upgrading is not immediately possible, restrict catalog.location.create permissions to trusted users only to reduce exposure.

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