VulnerabilityPublished 29 Oct 2026

CVE-2026-113713: virtualenv · Temporary app-data can leave dangling seed package links

Affects toxSource GCVE Database

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Authoritative record:CVE-2026-113713· Medium 4.4

Not known to be exploited · CVSS 4.4 Medium : upgrade to 4.67.0 when convenient.

Data as of 30 Oct 2026, 07:30 UTC

CVSS 4.0 base score

4.4Medium

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 4.0	4.4

Patch: Available – fixed in 4.67.0

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

Attack Vector: Local
Attack Complexity: High
Attack Requirements: Present
Privileges Required: Low
User Interaction: Passive
Vulnerable system confidentiality: Low
Vulnerable system integrity: High
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: Local: The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
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: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
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: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence 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
Weaponized: 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 29 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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 tox to 4.67.0.

Affected software

Product	Affected	Fixed in
Homebrewtox`pkg:brew/tox`Other threats	Affected >=4.66.0 <4.67.0	Fixed in 4.67.0

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

Description

## Summary The app-data seeder can leave an environment linked to temporary package files that virtualenv deletes when creation finishes. The environment-variable and configuration-file forms of `symlink_app_data` can enable this state even though the command-line flag is disabled for temporary app-data. The resulting environment depends on a cache pathname that its owner no longer controls. Anthropic's OSS Scanner reported this as `ANT-2026-ZOE2GEPC` in `virtualenv-20261015-005`, received on 15 October 2026. This draft records source review and functional remediation checks. The reporter's cross-account code-execution claim has not been independently reproduced. ## Affected area Integrity of app-data references after temporary cache cleanup. ## Attacker-controlled input Symlink seeding must be enabled through `VIRTUALENV_SYMLINK_APP_DATA` or `symlink_app_data` in the configuration file, and app-data setup must fall back to a temporary directory. A missing or unwritable configured cache can cause that fallback. Ordinary copy seeding does not leave these references. The security concern requires a shared temporary-directory parent where another account can acquire the deleted cache pathname, followed by use of the affected environment. That account need not already be able to modify the environment or the private cache while it exists. This differs from the security policy's excluded case of an account that already controls live app-data contents. On a platform with a temporary-directory parent private to the environment owner, that cross-account condition is absent. Windows functional checks do not establish cross-account exposure under Windows defaults. ## Affected code The relevant 21.14.8 source is in [symlink seeder](https://github.com/pypa/virtualenv/blob/a795ab116356afde11039cf2763d77e8a06da738/src/virtualenv/seed/embed/via_app_data/via_app_data.py), [temporary cache cleanup](https://github.com/pypa/virtualenv/blob/a795ab116356afde11039cf2763d77e8a06da738/src/virtualenv/app_data/via_tempdir.py). ## Mechanism When app-data setup falls back to a temporary directory, the command-line `--symlink-app-data` action is disabled. A value supplied by `VIRTUALENV_SYMLINK_APP_DATA` or `virtualenv.ini` can still become the parser default, and the seeder constructor accepts that value without rechecking the cache lifetime. It links `site-packages/pip` into the temporary cache. Session cleanup deletes that cache, leaving a dangling link whose pathname can later be claimed by another account on a shared temporary filesystem. ## Reproduction and evidence The scanner ran its reproduction as two unprivileged users, with root used only to switch identities. The environment owner had an unwritable home, so app-data fell back to `/tmp`. The control used the command-line flag and received a real pip directory. With `VIRTUALENV_SYMLINK_APP_DATA=1`, the new environment instead contained a `pip` link into a deleted `/tmp/tmpXXXXXXXX` directory. A second uid recreated the target path and placed a fake `pip/__init__.py` there. When the owner ran `venv/bin/pip --version`, that module created a marker inside the owner's environment and printed `this is not pip`. The cross-account path requires a shared temporary parent, a second account able to claim the deleted name, and later use of the environment. A private temporary parent removes that route. The report traces the incomplete temporary-cache guard to #1661, first released in 20.0.6. [Public fix PR #3437](https://github.com/pypa/virtualenv/pull/3437) copies packages whenever app-data is temporary, whatever supplied the symlink option. The implementation review checked the remediation; it did not rerun the cross-account reproduction. ## Attack sequence ```mermaid sequenceDiagram participant U as Environment owner participant V as virtualenv seeder participant T as Temporary app-data in /tmp participant E as site-packages/pip link participant A as Other local account U->>V: VIRTUALENV_SYMLINK_APP_DATA=1 with unwritable home V->>T: create transient cache V->>E: link pip to cache path V->>T: delete cache at session exit A->>T: reclaim old name and plant fake pip U->>E: run bin/pip --version E->>T: import fake pip through stale link T-->>U: attacker's code runs as owner ``` ## Reproducer files The following files are from the scanner report for `ANT-2026-ZOE2GEPC`. 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 os import pwd import shutil import subprocess from pathlib import Path owner = pwd.getpwnam("nobody") # home is /nonexistent: app-data cannot be create

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