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GHSA-p7q8-grrj-3m8w — copier

Fix: copier-org/copier@fdbc016

GHSA-p7q8-grrj-3m8w is a Path Traversal vulnerability in copier. A fix is available for copier — see the affected versions and patch details below.

Copier's safe template has filesystem write access outside destination path

Also known asCVE-2025-55214PYSEC-2026-1273
Published
Aug 18, 2025
Updated
Jul 7, 2026
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Sep 26, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.

Exploitation and automatability from CISA’s SSVC triage for GHSA-p7q8-grrj-3m8w.

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs16th percentile — riskier than 16% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected
🐍copier

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Impact

Copier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use unsafe features like custom Jinja extensions which would require passing the --UNSAFE,--trust flag. As it turns out, a safe template can currently write files outside the destination path where a project shall be generated or updated. This is possible when rendering a generated directory structure whose rendered path is either a relative parent path or an absolute path. Constructing such paths is possible using Copier's builtin pathjoin Jinja filter and its builtin _copier_conf.sep variable, which is the platform-native path separator. This way, a malicious template author can create a template that overwrites arbitrary files (according to the user's write permissions), e.g., to cause havoc.

Write access via generated relative path

Reproducible example:

echo "foo" > forbidden.txt
mkdir src/
echo "bar" > "src/{{ pathjoin('..', 'forbidden.txt') }}"
uvx copier copy src/ dst/
cat forbidden.txt

Write access via generated absolute path

Reproducible example:

  • POSIX:

    # Assumption: The current working directory is `/tmp/test-copier-vulnerability/`
    echo "foo" > forbidden.txt
    mkdir src/
    echo "bar" > "src/{{ pathjoin(_copier_conf.sep, 'tmp', 'test-copier-vulnerability', 'forbidden.txt') }}"
    uvx --from copier python -O -m copier copy --overwrite src/ dst/
    cat forbidden.txt
    
  • Windows (PowerShell):

    # Assumption: The current working directory is `C:\Users\<user>\Temp\test-copier-vulnerability`
    echo "foo" > forbidden.txt
    mkdir src
    Set-Content -Path src\copier.yml @'
    drive:
      type: str
      default: "C:"
      when: false
    '@
    echo "bar" > "src\{{ pathjoin(drive, 'Users', '<user>', 'Temp', 'test-copier-vulnerability', 'forbidden.txt') }}"
    uvx --from copier python -O -m copier copy --overwrite src dst
    cat forbidden.txt
    

This scenario is slightly less severe, as Copier has a few assertions of the destination path being relative which would typically be raised. But python -O (or PYTHONOPTIMIZE=x) removes asserts, so these guards may be ineffective. In addition, this scenario will prompt for overwrite confirmation or require the --overwrite flag for non-interactive mode; yet malicious file writes might go unnoticed.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIcopier≥ 7.1.0&&< 9.9.19.9.1pip install --upgrade 'copier==9.9.1'

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for copier, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update copier to 9.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-p7q8-grrj-3m8w is resolved across your whole dependency graph.

  3. Workarounds

    Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

  4. How O3 protects you

    O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-p7q8-grrj-3m8w can be triaged on real exposure rather than presence alone.

Tailored to GHSA-p7q8-grrj-3m8w. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Impact Copier suggests that it's safe to generate a project from a safe template, i.e. one that doesn't use [unsafe](https://copier.readthedocs.io/en/stable/configuring/#unsafe) features like custom Jinja extensions which would require passing the `--UNSAFE,--trust` flag. As it turns out, a safe template can currently write files outside the destination path where a project shall be generated or updated. This is possible when rendering a [generated directory structure](https://copier.readthedocs.io/en/stable/configuring/#generating-a-directory-structure) whose rendered path is either a re
O3 Security · Impact-Aware SCA

Is GHSA-p7q8-grrj-3m8w in your dependencies?

O3 Security finds GHSA-p7q8-grrj-3m8w across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.