GHSA-p58f-9548-mpm2: OS Command Injection
Impact
The generated activate (bash/zsh) and activate.fish scripts interpolate a shlex.quote-ed value into a position that quotes it a second time. The extra quotes terminate the quoted run early and leave part of the value parsed as shell code, so a path containing shell metacharacters runs commands when a user sources the activation script.
activate is affected through the virtual environment's own path, on the branch that reports a relocated environment:
sh echo "Virtual environment directory VIRTUALENV does not exist!" >&2
For a destination named x'$(id)'y, shlex.quote emits 'x'"'"'$(id)'"'"'y'. The inner " closes the enclosing double quote and $(id) is left unquoted. Backtick and ; payloads reach the same result. This branch runs whenever the recorded path is absent, which is the normal case for a virtual environment copied or distributed to another machine.
activate.fish is affected through the interpreter's Tcl/Tk library paths:
fish set -gx TCLLIBRARY 'TCLLIBRARY'
shlex.quote already returns '/tcl/(cmd)/lib', so the rendered line is ''/tcl/(cmd)/lib''. fish concatenates the adjacent quoted runs and expands the (cmd) left between them. The same doubling also splits a path containing a space into two list elements, corrupting TCLLIBRARY and TKLIBRARY.
This is the same defect class as GHSA-x78j-v8h9-3j2q, which covered activate.bat.
Patches
Fixed in 21.7.13 by moving the placeholders outside the surrounding quotes, so each value keeps only the quoting shlex.quote applied. Fix: https://github.com/pypa/virtualenv/pull/3252
Workarounds
Avoid creating or distributing virtual environments whose path contains ', , $, ;, ( or ), and inspect the generated activation script before sourcing one you did not create.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/virtualenvto a version that resolves this vulnerability.Fixed in 21.7.13 - Upgrade
Upgrade
virtualenvto a version that resolves this vulnerability.Fixed in 21.7.13 - Compensating control
Avoid creating or distributing virtual environments whose path contains ', `, $, ;, ( or ), and inspect any generated activation script before sourcing one you did not create.
Event History
Frequently Asked Questions
When is the Bash/Zsh activation script vulnerable in practice?
The vulnerable branch runs when the virtual environment's recorded path does not exist. This is the normal case when a virtual environment has been copied or distributed to another machine, and the destination path contains shell metacharacters.
What user interaction is required for exploitation?
A user must source the generated Bash/Zsh activation script or use the affected Fish activation script. Commands embedded in the relevant path value can then be parsed and executed by the shell.
Which paths can carry the malicious payload?
For Bash/Zsh, the virtual environment's own path is the affected value. For Fish, the affected values are the interpreter's Tcl/Tk library paths; command substitutions, backticks, and semicolon-based payloads are described as reaching shell execution.