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Response snapshot Oct 27, 2026, 02:11 UTC

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VulnerabilityCVE-2026-113714

virtualenv: Downloaded wheel selection and caching precede verification

Wheel downloads go directly into the reusable wheelhouse, while the verification target is selected from pip's textual output. A verification failure does not remove the downloaded file from that cache.

Published Updated

At a glance

Exploited
Not known
Severity
2.3 Low (CVSS 4.0)
Chance of exploitation
0.2% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: virtualenv: 21.14.9. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-494p-63j8-28p3 (opens a new tab)

What happened

## Summary

Wheel downloads go directly into the reusable wheelhouse, while the verification target is selected from pip's textual output. A verification failure does not remove the downloaded file from that cache.

Anthropic's OSS Scanner reported this as `ANT-2026-ST00DRO3` in `virtualenv-20261015-005`, received on 15 October 2026.

## Affected area

Continue reading

Download selection and promotion into the reusable wheel cache.

## Attacker-controlled input

A download must fail verification, or the archive selected from pip output must differ from the file later reused. Default-index digest verification must be enabled. Existing custom-index exceptions are outside the promised PyPI comparison.

## Affected code

The relevant 21.14.8 source is in [wheel download and digest check](https://github.com/pypa/virtualenv/blob/a795ab116356afde11039cf2763d77e8a06da738/src/virtualenv/seed/wheels/acquire.py).

## Mechanism

`download_wheel()` tells pip to write directly into the reusable `wheel/house` cache. It then selects a path to hash from the first `Saved ` line in pip's stdout, rather than from the file pip actually placed there. A package index can inject such a line through a discarded link's `data-requires-python` attribute.

A separate failure exists without the forged line: a digest mismatch raises after the downloaded wheel has entered the cache, and the rejected bytes remain there. Later wheel selection does not hash the cached file again.

## Reproduction and evidence

The scanner used a local index configured in `pip.conf`, with PyPI digest comparison still enabled. In the control case it served a modified pip wheel alone. `virtualenv --upgrade-embed-wheels` refused the mismatch, and a subsequent environment used the bundled pip. In the attack case the index added a link whose `data-requires-python` contained a forged `Saved ` line pointing at a genuine bundled wheel.

The upgrade then exited without a digest error, recorded the modified wheel in its update log, and a later environment's `pip --version` ran a line added by the index. The reproduction used a known absolute path to the genuine bundled wheel; that prerequisite is part of this variant.

The report also shows that a refused wheel can replace a previously accepted file of the same name in `wheel/house`, leaving rejected bytes available for later use. It does not claim to bypass TLS or affect the default PyPI setup. The gap follows the digest check added in #3251, first released in 21.7.12. [PR #3430](https://github.com/pypa/virtualenv/pull/3430) downloads to a private temporary directory, verifies the actual archive, and promotes it only after acceptance.

## Attack sequence

```mermaid sequenceDiagram participant I as Configured index participant P as pip download participant C as wheel/house cache participant V as virtualenv digest check participant N as New environment I->>P: modified wheel and forged Saved line P->>C: write modified wheel directly P-->>V: stdout names genuine bundled wheel V->>V: hash genuine wheel and accept V->>C: record modified wheel for reuse C->>N: seed modified pip without rehash Note over P,C: Even a rejected wheel can remain in the cache ```

## Reproducer files

The following files are from the scanner report for `ANT-2026-ST00DRO3`. They were tested against commit `a857a7823c73` in the scanner image. The `repro` entrypoint expects companion files under `/tmp/repro.d`; cases that change user IDs need a disposable root-capable container. The last output line is `BUG` when the reported behavior occurs. These files are included as evidence and were not rerun for this advisory update.

**`repro`**

```text #!/usr/bin/env python3 import atexit import hashlib import json import os import shutil import subprocess import sys from pathlib import Path

companions = Path("/tmp/repro.d") work = Path("/tmp/forged-saved-line") home = work / "home" app_data = home / ".cache" / "virtualenv" this_python = f"{sys.version_info.major}.{sys.version_info.minor}" # the target; each Python has its own update log update_log_of_pip = app_data / "wheel" / this_python / "embed" / "3" / "pip.json" virtualenv = [sys.executable, companions / "virtualenv_with_local_pypi_json.

py", work / "pypi"] as_user = {"cwd": home, "env": {"HOME": str(home), "PATH": os.environ["PATH"]}, "capture_output": True, "text": True} added_code_prints = "code added by the index" # the line index_serves_modified_pip.py adds to pip/__init__.py

def user_upgrades_seed_wheels_and_creates_env(): # each case starts from an empty app-data shutil.rmtree(app_data, ignore_errors=True) shutil.rmtree(home / "env", ignore_errors=True) upgrade = subprocess.run([*virtualenv, "--upgrade-embed-wheels"], **as_user) # --no-periodic-update: the background update is another process, which the PyPI stand-in does not reach subprocess.

run([*virtualenv, "--no-periodic-update", "env"], **as_user, check=True) pip_version = subprocess.run([home / "env" / "bin" / "python", "-m", "pip", "--version"], **as_user, check=True) # one thread per target Python; a refused wheel ends its thread with a traceback on stderr, the exit code stays 0 refusal = next((line for line in upgrade.stderr.

splitlines() if "but PyPI reports" in line), None) logged = [] if update_log_of_pip.exists(): # a failed update writes no log logged = [entry["filename"] for entry in json.loads(update_log_of_pip.read_text())["versions"]] return refusal, logged, pip_version.stdout.splitlines()

# set up: PyPI's answers, a faithful mirror of PyPI on 127.0.0.1:8099, a user whose pip.conf points pip at it shutil.rmtree(work, ignore_errors=True) (home / ".config" / "pip").mkdir(parents=True) shutil.copy(companions / "pip.conf", home / ".config" / "pip" / "pip.conf") subprocess.run([sys.executable, companions / "pypi_json_and_mirror.py", work / "pypi", work / "index"], check=True) index_server = subprocess.

Popen( [sys.executable, "-u", "-m", "http.server", "8099", "--bind", "127.0.0.1", "--directory", work / "

Affected package ranges reported by GitHub: virtualenv: < 21.14.9

Scores and how they were measured

CVSS base severity

2.3

Version 4.0As of

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.2%

Scored Percentile 12.3%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-494p-63j8-28p3 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-494p-63j8-28p3, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-113714, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 23). virtualenv: Downloaded wheel selection and caching precede verification (CVE-2026-113714). https://kevwire.com/record/CVE-2026-113714

MLA

"virtualenv: Downloaded wheel selection and caching precede verification (CVE-2026-113714)." KEVWire, 23 Oct. 2026, kevwire.com/record/CVE-2026-113714.

Chicago

KEVWire. "virtualenv: Downloaded wheel selection and caching precede verification (CVE-2026-113714)." Last modified October 23, 2026. https://kevwire.com/record/CVE-2026-113714.

Evidence summary (plain text)

virtualenv: Downloaded wheel selection and caching precede verification (Oct 23, 2026).
Wheel downloads go directly into the reusable wheelhouse, while the verification target is selected from pip's textual
output. A verification failure does not remove the downloaded file from that cache.

Anthropic's OSS Scanner reported this as `ANT-2026-ST00DRO3` in `virtualenv-20261015-005`, received on 15 October 2026.
CVSS 2.3 (version 4.0; evidence as of Oct 23, 2026; https://github.com/advisories/GHSA-494p-63j8-28p3).
EPSS 0.2% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-113714&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-494p-63j8-28p3: https://github.com/advisories/GHSA-494p-63j8-28p3
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-113714&date=2026-10-26
Record ID: CVE-2026-113714.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 01:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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