VulnerabilityPublished 26 Oct 2026

CVE-2026-113720: virtualenv · Seeded files retain permissions from an older cache

Affects toxSource GCVE Database

Authoritative record:CVE-2026-113720· Medium 4.4

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

Data as of 27 Oct 2026, 06:44 UTC

CVSS 4.0 base score

4.4Medium

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

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
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 tox to 4.67.0.

Affected software

Product	Affected	Fixed in
Homebrewtox`pkg:brew/tox`Other threats	Affected >=3.14.5_1 <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.

AI-suggested

A fix is available in virtualenv version 4.67.0, which enforces stricter file permissions on copied files, preventing retention of overly permissive modes from the cache. Users should upgrade to version 4.67.0 or later to remediate this issue. Until upgraded, ensure that the cache is created with restrictive permissions and that environments are not accessible to untrusted local users. No other specific mitigations are indicated by the vendor advisory.

Description

CVE-2026-113720 is a vulnerability in virtualenv where files copied from a cached app-data directory retain file permissions from an earlier environment, potentially resulting in files with broader access than intended. This occurs because shutil.copy preserves the cached file modes regardless of the current umask. An attacker with access to the new environment can exploit this if the cache was created under permissive permissions and the new environment is accessible to other local accounts. The issue was identified in virtualenv versions starting from 20.0.2 and fixed in version 4.67.0.

Impact

Files in virtualenv environments created from a cached app-data directory may have broader permissions than intended, allowing other local users to modify files within the environment. This can lead to privilege escalation or code execution as the environment owner if an attacker appends malicious code to writable files like pip/__init__.py. The vulnerability requires that the cache was created under permissive permissions and that the new environment is accessible to other local accounts. The cache directory itself remains private, limiting the attack surface to environments reachable by other users.

Summary

The vulnerability arises from the app-data copy seeder in virtualenv using shutil.copy, which preserves the source file mode from the cache when copying files into new environments. If the cache was populated under a permissive umask (e.g., 000), files copied into later environments can have overly broad permissions (e.g., mode 0666), even if the new environment uses a more restrictive umask (e.g., 022). This can allow other local users to modify files such as pip/__init__.py, leading to code execution as the environment owner. The cache itself remains private, so exploitation requires the new environment to be accessible by other local accounts. The vulnerability was reported by Anthropic's OSS Scanner and affects virtualenv versions from 20.0.2 until fixed in 4.67.0 by PR #3425, which enforces stricter file permissions on copied files.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 27 Oct 2026, 06:44 UTC

Technical details

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