CVE-2026-102938
MediumCVSS 5.8Summary
virtualenv is a tool for creating isolated virtual Python environments. Prior to 21.7.11, PyEnvCfg.write() writes prompt values verbatim to the line-oriented pyvenv.cfg format while PyEnvCfg._read_values() parses the file with str.splitlines() and accepts the last value for duplicate keys. An attacker who influences --prompt, VIRTUALENV_PROMPT, or configuration input can insert a recognized line boundary and additional keys, including home, causing consumers to use an attacker-selected base interpreter or corrupted environment metadata.
Risk Assessment
An attacker could cause the use of a malicious base interpreter or corrupt environment metadata, potentially leading to execution of untrusted code. However, this requires influence over prompt input from outside the operator's trust boundary.
Recommendation
Upgrade virtualenv to version 21.7.11 or later. Avoid passing untrusted input to the --prompt or VIRTUALENV_PROMPT options.
Other vulnerabilities in virtualenv
See all- CVE-2026-102937High
In virtualenv prior to 21.7.12, BatchActivator.quote() returns prompt text unchanged before activate.bat inserts it into a cmd.exe set "VAR=value" statement. An attacker who influences --prompt, VIRTUALENV_PROMPT, or the corresponding configuration value can include a double quote that closes the assignment and leaves following cmd.exe operators as executable syntax. When a user activates the generated Windows environment, the injected commands run with that user's privileges.
- CVE-2026-102930High
In virtualenv prior to 21.7.12, download_wheel() accepts pip and setuptools seed wheels fetched for periodic updates or the --download option without checking their bytes against an authoritative digest equivalent to the embedded wheels' BUNDLE_SHA256 verification. A compromised index, stale mirror, or intercepted TLS connection can substitute a different wheel under the requested distribution, version, and filename, after which virtualenv caches and seeds the attacker-controlled wheel into subsequently created environments. The verification applies to the default PyPI path and is intentionally skipped when PIP_INDEX_URL, PIP_EXTRA_INDEX_URL, or PIP_INDEX configures a custom index.
- CVE-2026-102925High
In virtualenv prior to 21.7.13, the generated activate (bash and zsh) and activate.fish scripts place values already escaped by shlex.quote inside an additional quoted context. In the bash and zsh script, a crafted virtual environment path reaches __VIRTUAL_ENV__ when a relocated environment's recorded directory is absent; in the fish script, crafted Tcl or Tk library paths reach __TCL_LIBRARY__ or __TK_LIBRARY__. The surplus quotes can terminate the data-only quoted run and leave shell metacharacters parsed as commands when a user sources the activation script, allowing code execution with that user's privileges.
Original NVD description (English source)
virtualenv is a tool for creating isolated virtual python environments. Prior to 21.7.11, PyEnvCfg.write() writes prompt values verbatim to the line-oriented pyvenv.cfg format while PyEnvCfg._read_values() parses the file with str.splitlines() and accepts the last value for duplicate keys. An attacker who influences --prompt, VIRTUALENV_PROMPT, or configuration input can insert a recognized line boundary and additional keys, including home, causing consumers to use an attacker-selected base interpreter or corrupted environment metadata. The security impact requires prompt input from outside the operator's trust boundary; directly supplied prompt content primarily corrupts the operator's own environment. This issue is fixed in version 21.7.11.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS