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Weblate: Prefix-Based Repository Boundary Check Bypass via Symlink/Junction Path Prefix Collision

Moderate severity GitHub Reviewed Published Apr 15, 2026 in WeblateOrg/weblate

Package

pip weblate (pip)

Affected versions

< 5.17

Patched versions

5.17

Description

Impact

Weblate repository-boundary validation relies on string prefix checks on resolved absolute paths. In multiple code paths, the check uses startswith against the repository root path. This is not path-segment aware and can be bypassed when the external path shares the same string prefix as the repository path (for example, repo and repo_outside).

Patches

References

Thanks to m9nx4u for reporting this issue via HackerOne.

References

@nijel nijel published to WeblateOrg/weblate Apr 15, 2026
Published by the National Vulnerability Database Apr 15, 2026
Published to the GitHub Advisory Database Apr 16, 2026
Reviewed Apr 16, 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
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
Low
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:L/PR:L/UI:N/S:C/C:L/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.
(4th percentile)

Weaknesses

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

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. Learn more on MITRE.

CVE ID

CVE-2026-40256

GHSA ID

GHSA-ffgh-3jrf-8wvh

Source code

Credits

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