pypa virtualenv up to 21.14.1 Template Instantiation activate_this.py ViaTemplateActivator.instantiate_template prompt code injection

Summaryinfo

A vulnerability has been found in pypa virtualenv up to 21.14.1 and classified as problematic. Affected by this issue is the function ViaTemplateActivator.instantiate_template of the file activate_this.py of the component Template Instantiation. Performing a manipulation of the argument prompt results in code injection. This vulnerability is reported as CVE-2026-113776. The attack requires a local approach. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as problematic, was found in pypa virtualenv up to 21.14.1. This affects the function ViaTemplateActivator.instantiate_template of the file activate_this.py of the component Template Instantiation. The manipulation of the argument prompt with an unknown input leads to a code injection vulnerability. CWE is classifying the issue as CWE-94. The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

virtualenv is a tool for creating isolated virtual python environments. From 20.26.6 until 21.14.2, ViaTemplateActivator.instantiate_template() replaces placeholders one key at a time across the complete activation template, so trigger names such as __VIRTUAL_NAME__, __VIRTUAL_ENV__, or __VIRTUAL_PROMPT__ inside an already substituted and quoted environment path or prompt can be replaced during a later pass. The later value's quoting can close the earlier literal and execute the remaining path when a user activates the environment through bash, fish, xonsh, or activate_this.py. The distinct csh prompt-display token __VIRTUAL_PROMPT_DISPLAY_TCSH__ can instead break the generated script without establishing command execution. The attacker must influence the destination path or --prompt, and a value without a relevant placeholder name does not trigger this mechanism. This issue is fixed in version 21.14.2.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-113776 since 10/20/2026. The exploitability is told to be easy. An attack has to be approached locally. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1059 for this issue.

Upgrading to version 21.14.2 eliminates this vulnerability.

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Productinfo

Vendor

• pypa

Name

• virtualenv

Version

• 21.14.0
• 21.14.1

Website

• Product: https://github.com/pypa/virtualenv/

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