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@backstage/cli-common has a possible `resolveSafeChildPath` Symlink Chain Bypass

Moderate severity GitHub Reviewed Published Jan 21, 2026 in backstage/backstage • Updated Jan 22, 2026

Package

npm @backstage/cli-common (npm)

Affected versions

<= 0.1.16

Patched versions

0.1.17

Description

Impact

The resolveSafeChildPath utility function in @backstage/backend-plugin-api, which is used to prevent path traversal attacks, failed to properly validate symlink chains and dangling symlinks. An attacker could bypass the path validation by:

  1. Symlink chains: Creating link1 → link2 → /outside where intermediate symlinks eventually resolve outside the allowed directory
  2. Dangling symlinks: Creating symlinks pointing to non-existent paths outside the base directory, which would later be created during file operations

This function is used by Scaffolder actions and other backend components to ensure file operations stay within designated directories.

Patches

This vulnerability is fixed in @backstage/backend-plugin-api version 0.1.17. Users should upgrade to this version or later.

Workarounds

  • Run Backstage in a containerised environment with limited filesystem access
  • Restrict template creation to trusted users

References

@Rugvip Rugvip published to backstage/backstage Jan 21, 2026
Published to the GitHub Advisory Database Jan 21, 2026
Reviewed Jan 21, 2026
Published by the National Vulnerability Database Jan 21, 2026
Last updated Jan 22, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(3rd percentile)

Weaknesses

Improper Link Resolution Before File Access ('Link Following')

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource. Learn more on MITRE.

UNIX Symbolic Link (Symlink) Following

The product, when opening a file or directory, does not sufficiently account for when the file is a symbolic link that resolves to a target outside of the intended control sphere. This could allow an attacker to cause the product to operate on unauthorized files. Learn more on MITRE.

CVE ID

CVE-2026-24047

GHSA ID

GHSA-2p49-45hj-7mc9

Source code

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