What’s Vulnerable › Vulnerabilities

CVE-2026-34726: Copier `_subdirectory` allows template root escape via parent-directory traversal

• Severity: medium (CVSS 4.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-04-02 · updated 2026-07-24
• Weakness: CWE-22

Description

Copier is a library and CLI app for rendering project templates. Prior to version 9.14.1, Copier's _subdirectory setting is documented as the subdirectory to use as the template root. However, the current implementation accepts parent-directory traversal such as .. and uses it directly when selecting the template root. As a result, a template can escape its own directory and make Copier render files from the parent directory without --UNSAFE. This issue has been patched in version 9.14.1.

Affected products

• copier-org copier: before 9.14.1 — fixed in 9.14.1

How to fix

Upgrade to a fixed version: copier-org copier 9.14.1. Check the vendor advisory for mitigations.

References

• https://github.com/copier-org/copier/commit/cb80a3ffc9c3787de3ed837e04ca29a0ff8ca3df
• https://github.com/copier-org/copier/releases/tag/v9.14.1
• https://github.com/copier-org/copier/security/advisories/GHSA-85v3-4m8g-hrh6
• https://github.com/copier-org/copier/security/advisories/GHSA-85v3-4m8g-hrh6

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