Affected: Homebrew: cloudiscovery

`download_wheel()` runs `pip download` and hands the result straight to the seeder, with nothing checking the bytes it gets back. The embedded pip and setuptools wheels carry a `BUNDLE_SHA256` that virtualenv checks on every load, but a wheel fetched over the network for the periodic-update feature or the `--download` flag had no equivalent verification.

A compromised index, a stale mirror, or a MITM'd download (when TLS is intercepted, e.g. via a misconfigured or malicious CA) could substitute a different wheel under the same distribution/version/filename, and virtualenv would cache and seed it into every environment created afterward with no warning.

Fixed in 21.7.12 by computing the downloaded wheel's sha256 and comparing it against the digest PyPI's public JSON API reports for that exact release, independent of which index actually served the file. The check is skipped, not treated as failure, when a custom index (`PIP_INDEX_URL`, `PIP_EXTRA_INDEX_URL`, `PIP_INDEX`) is configured, since a private index can legitimately serve a different, intentionally rebuilt wheel.

Affected: pypa virtualenv

virtualenv is a tool for creating isolated virtual python environments. Prior to 21.7.12, download_wheel() accepts pip and setuptools seed wheels fetched for periodic updates or the --download option without checking their bytes against an authoritative digest equivalent to the embedded wheels' BUNDLE_SHA256 verification. A compromised index, stale mirror, or intercepted TLS connection can substitute a different wheel under the requested distribution, version, and filename, after which virtualenv caches and seeds the attacker-controlled wheel into subsequently created environments. The verification applies to the default PyPI path and is intentionally skipped when PIP_INDEX_URL, PIP_EXTRA_INDEX_URL, or PIP_INDEX configures a custom index that may legitimately publish rebuilt wheels. This issue is fixed in version 21.7.12.

Affected: PyPI: virtualenv

`download_wheel()` runs `pip download` and hands the result straight to the seeder, with nothing checking the bytes it gets back. The embedded pip and setuptools wheels carry a `BUNDLE_SHA256` that virtualenv checks on every load, but a wheel fetched over the network for the periodic-update feature or the `--download` flag had no equivalent verification.

A compromised index, a stale mirror, or a MITM'd download (when TLS is intercepted, e.g. via a misconfigured or malicious CA) could substitute a different wheel under the same distribution/version/filename, and virtualenv would cache and seed it into every environment created afterward with no warning.

Fixed by computing the downloaded wheel's sha256 and comparing it against the digest PyPI's public JSON API reports for that exact release, independent of which index actually served the file. The check is skipped, not treated as failure, when a custom index (`PIP_INDEX_URL`, `PIP_EXTRA_INDEX_URL`, `PIP_INDEX`) is configured, since a private index can legitimately serve a different, intentionally rebuilt wheel. Fix: https://github.com/pypa/virtualenv/pull/3251