CVE-2024-9287

A vulnerability has been found in the CPython venv module and CLI where path names provided when creating a virtual environment were not quoted properly, allowing the creator to inject commands into virtual environment activation scripts (ie source venv/bin/activate). This means that attacker-controlled virtual environments are able to run commands when the virtual environment is activated. Virtual environments which are not created by an attacker or which arent activated before being used (ie ./venv/bin/python) are not affected.

Weakness

The product uses a search path that contains an unquoted element, in which the element contains whitespace or other separators. This can cause the product to access resources in a parent path.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

References

• https://github.com/python/cpython/commit/633555735a023d3e4d92ba31da35b1205f9ecbd7
• https://github.com/python/cpython/commit/8450b2482586857d689b6658f08de9c8179af7db
• https://github.com/python/cpython/commit/9286ab3a107ea41bd3f3c3682ce2512692bdded8
• https://github.com/python/cpython/commit/ae961ae94bf19c8f8c7fbea3d1c25cc55ce8ae97
• https://github.com/python/cpython/commit/d48cc82ed25e26b02eb97c6263d95dcaa1e9111b
• https://github.com/python/cpython/commit/e52095a0c1005a87eed2276af7a1f2f66e2b6483
• https://github.com/python/cpython/issues/124651
• https://github.com/python/cpython/pull/124712
• https://mail.python.org/archives/list/security-announce@python.org/thread/RSPJ2B5JL22FG3TKUJ7D7DQ4N5JRRBZL/