VulnerabilityPublished 26 Oct 2026

CVE-2026-113717: virtualenv · Pip seeding with download omits wheel digest verification

Affects noxSource GCVE Database

Authoritative record:CVE-2026-113717· Low 2.3

Not known to be exploited · CVSS 2.3 Low : upgrade to 2026.10.20 when convenient.

Data as of 27 Oct 2026, 06:43 UTC

CVSS 4.0 base score

2.3Low

How severe the flaw is on the 0–10 CVSS scale.

Patch: Available – fixed in 2026.10.20

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

Attack Vector: Network
Attack Complexity: High
Attack Requirements: Present
Privileges Required: None
User Interaction: Passive
Vulnerable system confidentiality: Low
Vulnerable system integrity: Low
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: The successful attack depends on the evasion or circumvention of security-enhancing techniques in place that would otherwise hinder the attack. These include: Evasion of exploit mitigation techniques, for example, circumvention of address space randomization (ASLR) or data execution prevention (DEP) must be performed for the attack to be successful; Obtaining target-specific secrets. The attacker must gather some target-specific secret before the attack can be successful. A secret is any piece of information that cannot be obtained through any amount of reconnaissance. To obtain the secret the attacker must perform additional attacks or break otherwise secure measures (e.g. knowledge of a secret key may be needed to break a crypto channel). This operation must be performed for each attacked target.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 20 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade nox to 2026.10.20.

Affected software

Product	Affected	Fixed in
Homebrewnox`pkg:brew/nox`Other threats	Affected >=2026.8.17_1 <2026.10.20	Fixed in 2026.10.20

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

## Summary The pip seeder acquires bundled wheels with download=False and lets pip access the index when --download is selected. Index candidates on that path do not pass through virtualenv's wheel digest verification. Anthropic's OSS Scanner reported this as `ANT-2026-74ALJBUF` in `virtualenv-20261015-005`, received on 15 October 2026. ## Affected area Wheel selection by the pip seeder when downloads are enabled. ## Attacker-controlled input The pip seeder and download option must be selected. The finding concerns the default-index digest-verification policy. Explicit custom-index settings already opt out of comparison against PyPI metadata; this patch retains that policy. ## Affected code The relevant 21.14.8 source is in [pip seeder](https://github.com/pypa/virtualenv/blob/a795ab116356afde11039cf2763d77e8a06da738/src/virtualenv/seed/embed/pip_invoke.py). ## Mechanism With `--seeder pip --download`, `PipInvoke.get_pip_install_cmd()` first calls `get_wheel(download=False)`, so virtualenv's `download_wheel()` and `verify_wheel_digest()` are skipped. It then lets `pip install` consult the configured index. An index wheel with the same package and version as the bundled wheel can be selected without virtualenv comparing its SHA-256 with PyPI metadata. The default app-data seeder takes the verification path for the same option. ## Reproduction and evidence The scanner built a local index named in `pip.conf` that served a modified copy of the bundled pip wheel under the same filename. In the control run, `virtualenv --download env-default` rejected the wheel with a digest mismatch. In the second run, adding `--seeder pip` produced an environment whose installed `pip/__init__.py` matched the index wheel; `env-pip/bin/pip --version` ran the added line. The reproducer checked the installed bytes and marker before reporting `BUG`. Both `--seeder pip` and `--download` are needed. The report used a non-PyPI index from `pip.conf` and left `PIP_INDEX_URL`, `PIP_EXTRA_INDEX_URL`, and `PIP_INDEX` unset, so virtualenv's default-seeder PyPI comparison remained active. This does not establish index control in the default PyPI setup. The unchecked pip-seeder download path is older, while the comparison with the default seeder arose when digest verification was added in 21.7.12. [PR #3430](https://github.com/pypa/virtualenv/pull/3430) acquires and verifies selected wheels before invoking pip with index lookup disabled. ## Attack sequence ```mermaid sequenceDiagram participant I as Index in pip.conf participant V as virtualenv PipInvoke participant P as pip install participant E as Seeded environment I->>V: serve modified pip wheel V->>V: get_wheel(download=False) V->>P: install with --download permitting index lookup P->>I: select same-version index wheel I->>E: modified pip installed without virtualenv digest check E->>E: later pip invocation runs added code Note over V,E: Default app-data seeder rejects the same digest ``` ## Reproducer files The following files are from the scanner report for `ANT-2026-74ALJBUF`. 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 glob import hashlib import json import os import shutil import subprocess import sys import zipfile from virtualenv.seed.wheels.embed import get_embed_wheel companions = "/tmp/repro.d" work = "/tmp/repro-pip-seeder-download" shutil.rmtree(work, ignore_errors=True) os.makedirs(work) # set up: the pip wheel virtualenv bundles, and PyPI's record of its sha256 (served by virtualenv_offline.py: no network) bundled = get_embed_wheel("pip", f"{sys.version_info.major}.{sys.version_info.minor}") pypi_sha256 = hashlib.sha256(open(bundled.path, "rb").read()).hexdigest() pypi_release = {"filename": bundled.name, "digests": {"sha256": pypi_sha256}} os.makedirs(f"{work}/pypi.org/pypi/pip") with open(f"{work}/pypi.org/pypi/pip/json", "w") as pypi_json: json.dump({"releases": {bundled.version: [pypi_release]}}, pypi_json) # attacker: the mirror serves other bytes under the bundled wheel's own file name marker = f"{work}/MIRROR_CODE_RAN" subprocess.run([sys.executable, f"{companions}/make_mirror.py", str(bundled.path), f"{work}/mirror", marker], check=True) mirror_wheel = f"{work}/mirror/pip/{bundled.name}" mirror_sha256 = hashlib.sha256(open(mirror_wheel, "rb").read()).hexdigest() print(f"{bundled.name}: PyPI publishes sha256 {pypi_sha256}") print(f"{bundled.name}: the mirror serves sha256 {mirror_sha256}") # user: pip.conf names the mirror; PIP_INDEX_URL, PIP_EXTRA_INDEX_URL and PIP_INDEX (which turn the check off) are unset with open(f"{work}/pip.conf", "w") a

References

Community reviews

Loading reviews…