fkie_cve-2026-113724

virtualenv is a tool for creating isolated virtual python environments. Prior to 21.14.9, the safe_delete() deletion error handler responds to a failed removal by reading mode bits with os.lstat(path) and applying owner-write permission with os.chmod(path, ...), which follows a symlink. A planted link inside a read-only directory can therefore cause a victim-owned target outside the destination that is initially not writable by the invoking user to become broadly writable before the retry fails, provided that user owns the target and can change its mode. Another account can use the widened mode only if it can traverse the target's parent directories; root does not reach the demonstrated failure path, and the operation does not itself read the target. This issue is fixed in version 21.14.9.

GHSA-43mp-35q3-x3fq — virtualenv: Deletion recovery can change a symlink target's mode

Affected: PyPI: virtualenv

## Summary

The deletion error handler obtains permission bits with lstat() but applies them through chmod(), which follows symlinks. On an eligible unlink failure this can change permissions outside the destination.

Anthropic's OSS Scanner reported this as `ANT-2026-UK90QC27` in `virtualenv-20261015-005`, received on 15 October 2026.

## Affected area

Permission recovery after a filesystem deletion error.

## Attacker-controlled input

A deletion must fail on a symbolic-link entry and enter the permission-recovery branch. The invoking user must have permission to change the target mode. This is conditional error handling, not the normal successful unlink path.

## Affected code

The relevant 21.14.8 source is in [safe_delete()](https://github.com/pypa/virtualenv/blob/a795ab116356afde11039cf2763d77e8a06da738/src/virtualenv/util/path/_sync.py).

## Mechanism

`safe_delete()` asks `shutil.rmtree()` to retry a failed removal after adding owner-write permission. Its error handler calls `os.lstat(path)` for mode bits but `os.chmod(path, ...)` to apply them. For a symlink, `lstat` reads the link's mode while `chmod` follows the link. A link inside a read-only directory can therefore cause the target's mode to become `0777` before the retry fails. The target must be owned by the invoking user and initially not writable by that user; root does not reach this failure path.

## Reproduction and evidence

The scanner packed a project containing a mode-`0555` `venv/bin/python/` direct…

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fkie_cve-2026-113724

GHSA-43mp-35q3-x3fq — virtualenv: Deletion recovery can change a symlink target's mode