virtualenv: Bash activator leaves the --prompt value unescaped in PS1 when promptvars is off, so prompt expansion later executes it (regression in 21.14.9)

virtualenv is a tool for creating isolated virtual python environments. From 21.14.9 until 21.14.13, the bash bin/activate script can copy an attacker-controlled --prompt value into PS1 without escaping dollar signs or backticks when both promptvars and POSIX mode are disabled during activation. Re-enabling promptvars, running set -o posix, or starting an interactive child bash that inherits the exported PS1 can then expand command substitution in the stored VIRTUAL_ENV_PROMPT value and execute commands as the user who activates the environment. This issue is fixed in version 21.14.13.

Source published

23 Oct 2026 19:34:46 UTC

Source modified

23 Oct 2026 20:55:42 UTC

Observed here

23 Oct 2026 21:48:20 UTC

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CVSS 4.0 · 7.1 CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N