vulnerability / NVI-00015116 / Revision 1
Copier has a trust-prefix bypass via path traversal that runs tasks unprompted
GitHub lists this reviewed advisory for copier. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
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02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
copier
source listed>= 9.5.0, <= 9.15.1
# Copier: trust-prefix bypass via path traversal runs tasks unprompted ### Summary In copier `>= 9.5.0, <= 9.15.1`, the `trust` setting's prefix match (`copier/_settings.py`) compares the template URL against a trusted prefix with a raw `str.startswith` and **no path normalization**, while the URL *is* normalized when the template is actually fetched (`Path.resolve()` for local paths; libcurl dot-segment removal for `https`). A template reference that textually starts with a trusted prefix but contains `..` (e.g. `https://github.com/trusted-org/../attacker-org/repo.git`) is therefore granted trust yet resolves to a different, attacker-controlled template, whose `tasks` / `migrations` / `jinja_extensions` then run **without the `--trust` prompt** — arbitrary command execution. Likely **CWE-22 (Improper Limitation of a Pathname)** in the trust check leading to **CWE-94 (code execution)**. ### Details `trust` lets users mark template locations as trusted so copier skips the unsafe-feature gate. A trailing `/` makes an entry a **prefix** match (`docs/settings.md`: *"Locations ending with `/` will be matched as prefixes, trusting all templates from that location"*). `copier/_settin
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-9gmc-jqmh-3rvm ↗
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Public revision history
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- Revision 1 ·
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