CVE-2026-113723 pypa CVE debrief

Who should care

Defenders responsible for Bash environments with compatibility level 4.2, users of virtualenv versions prior to 21.14.9, and teams managing packages and dependencies should assess exposure and verify upgrades.

Why it matters

CVE-2026-113723 allows code execution in virtualenv's Bash activation script under specific conditions. Defenders should assess exposure in Bash environments with compatibility level 4.2, verify 21.14.9 upgrade, and monitor for suspicious prompt behavior.

• Code execution in Bash environments with compatibility level 4.2
• Potential for attacker-influenced prompt text
• Verification of 21.14.9 upgrade required
• Monitoring for suspicious prompt behavior necessary

Technical summary

The virtualenv Bash activation script copies user-supplied prompt text into PS1 without proper escaping under Bash compatibility level 4.2. This allows an attacker to influence the prompt text and potentially execute code when a user activates the environment and draws the prompt. The issue is specific to POSIX activation and Bash runs with compatibility level 4.2. The vulnerability exists in virtualenv's Bash activation script, where user-supplied prompt text can be interpreted as executable syntax under older Bash compatibility modes.

Defensive priority

Assess exposure in Bash environments with compatibility level 4.2, verify 21.14.9 upgrade, and monitor for suspicious prompt behavior

Recommended defensive actions

• Assess Bash environment exposure with compatibility level 4.2
• Verify virtualenv version 21.14.9 upgrade
• Monitor for suspicious prompt behavior
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability exists in virtualenv's Bash activation script, where user-supplied prompt text can be interpreted as executable syntax under older Bash compatibility modes. The issue is specific to POSIX activation and Bash runs with compatibility level 4.2.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.