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PYSEC-2026-4013
virtualenvThe 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 (Virtual environment directory __VIRTUAL_ENV__ does not exist!). 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. 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
(set -gx TCL_LIBRARY '__TCL_LIBRARY__'). The rendered line becomes
''/tcl/(cmd)/lib'', and fish expands the (cmd) left between the adjacent
quoted runs. The same doubling splits a path containing a space into two list
elements, corrupting TCL_LIBRARY and TK_LIBRARY.
This is the same defect class as GHSA-x78j-v8h9-3j2q, which covered
activate.bat.
Fixed in 21.7.13 by moving the placeholders outside the surrounding quotes, so
each value keeps only the quoting shlex.quote applied.
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The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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