virtualenv CVE-2026-102937

Requires all of: virtualenv version prior to 21.7.12; the Windows platform, because the flaw is only in the cmd.exe activate.bat batch activator that inserts the prompt into a set "VAR=value" statement; attacker influence over the --prompt argument, the VIRTUALENV_PROMPT environment variable, or the corresponding prompt configuration value (the injection carrier is a double quote plus cmd.exe operators); and a victim who then generates and activates that environment. Limiting factors: local vector only, mandatory user interaction (running activate.bat), Windows-only, and the attacker must first get a hostile value into the prompt input - non-Windows activators and default/attacker-uncontrolled prompts are not affected.

This is a genuine but conditionally-gated command-injection flaw (CWE-78) in the ubiquitous PyPA virtualenv tool, specific to the Windows batch activator. The vendor CVSS 4.0 vector (AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H = 7.3) is internally consistent with the description: exploitation is local, requires a passive attack precondition (AT:P - the attacker must first get a malicious value into --prompt, VIRTUALENV_PROMPT, or the prompt config), and requires the victim to activate the generated environment (UI:P). The technical impact is severe (full C/I/A on the activating user) because arbitrary cmd.exe operators execute with the user's privileges, but the local vector plus mandatory user interaction plus attacker-influence precondition sharply limit real-world reach - this is not a remote, wormable bug. No EPSS score, no CISA KEV listing, and no public exploit code are present in the provided data, so exploitation status is: no public exploit identified at time of analysis. Net: a real, patch-worthy issue for Windows Python developers/CI, but a targeted/supply-chain-flavored risk rather than mass-exploitable - priority is moderate. The vendor CVSS scores it as HIGH; I concur that severity-when-triggered is high while likelihood is constrained.

An attacker seeds a shared repository, template, or environment with a crafted prompt value (e.g. a malicious .cfg prompt setting or an exported VIRTUALENV_PROMPT) containing a double quote that closes the cmd.exe set assignment followed by executable operators. A Windows developer or CI job using virtualenv < 21.7.12 creates the environment and runs activate.bat, at which point the injected commands execute with that user's privileges. No public exploit code is identified, but the injection is straightforward given control of the prompt input.