CVE-2026-113715: virtualenv: Venv configuration readback can reinterpret path boundaries

Q: Who is realistically exposed to this issue?

Deployments using virtualenv versions earlier than 21.14.9 are affected only when they use the stdlib venv creator and allow an untrusted party to influence the destination pathname. The builtin creator does not use the vulnerable readback path.

Q: What does an attacker need to exploit it?

The attacker must be able to supply or influence the virtual-environment destination pathname so it contains a line-boundary character such as U+2028. Changing the home setting also requires the attacker to control the referenced location to influence which standard-library files the interpreter loads.

Q: What is the practical impact of injected configuration values?

An injected include-system-site-packages=true value weakens the isolation of the created environment. An altered home value can redirect the interpreter's standard-library lookup when the attacker controls that location.

Q: What should be done if upgrading is not immediately possible?

Do not allow untrusted input to control virtual-environment destination pathnames, particularly pathnames containing line-boundary characters. Where possible, avoid the stdlib venv creator, since the builtin creator does not use the affected readback behavior.

Published Oct 20, 2026

Updated

virtualenv is a tool for creating isolated virtual python environments. Prior to 21.14.9, the stdlib venv creator reads generated pyvenv.cfg with str.splitlines() and merges parsed keys over virtualenv's selected configuration. An untrusted caller who influences the destination pathname can include a line-boundary character such as U+2028 to inject keys including home and include-system-site-packages, causing path data to change configuration structure before final output. Setting include-system-site-packages to true weakens environment isolation, while an altered home can change which standard-library files the interpreter loads if the attacker also controls that location. The builtin creator does not use this readback path. This issue is fixed in version 21.14.9.

Affected Software

1 affected component

pypi/virtualenv<21.14.9

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
Upgrade virtualenv to a version that resolves this vulnerability.
Fixed in 21.14.9

Event History

Oct 20, 2026

CVE Published

via MITRE·07:42 PM

Data Sourced

via MITRE·07:42 PM

DescriptionWeakness

Data Sourced

via NVD·08:17 PM

DescriptionSeverityWeakness

Frequently Asked Questions

Who is realistically exposed to this issue?

Deployments using virtualenv versions earlier than 21.14.9 are affected only when they use the stdlib venv creator and allow an untrusted party to influence the destination pathname. The builtin creator does not use the vulnerable readback path.

What does an attacker need to exploit it?

The attacker must be able to supply or influence the virtual-environment destination pathname so it contains a line-boundary character such as U+2028. Changing the home setting also requires the attacker to control the referenced location to influence which standard-library files the interpreter loads.

What is the practical impact of injected configuration values?

An injected include-system-site-packages=true value weakens the isolation of the created environment. An altered home value can redirect the interpreter's standard-library lookup when the attacker controls that location.

What should be done if upgrading is not immediately possible?

Do not allow untrusted input to control virtual-environment destination pathnames, particularly pathnames containing line-boundary characters. Where possible, avoid the stdlib venv creator, since the builtin creator does not use the affected readback behavior.

CVE-2026-113715: virtualenv: Venv configuration readback can reinterpret path boundaries

Affected Software

Remediation

Event History

Frequently Asked Questions

Who is realistically exposed to this issue?

What does an attacker need to exploit it?

What is the practical impact of injected configuration values?

What should be done if upgrading is not immediately possible?

Company

Resources

Contact

Frequently Asked Questions

Who is realistically exposed to this issue?

What does an attacker need to exploit it?

What is the practical impact of injected configuration values?

What should be done if upgrading is not immediately possible?