CVE-2022-21668

pipenv is a Python development workflow tool. Starting with version 2018.10.9 and prior to version 2022.1.8, a flaw in pipenvs parsing of requirements files allows an attacker to insert a specially crafted string inside a comment anywhere within a requirements.txt file, which will cause victims who use pipenv to install the requirements file to download dependencies from a package index server controlled by the attacker. By embedding malicious code in packages served from their malicious index server, the attacker can trigger arbitrary remote code execution (RCE) on the victims systems. If an attacker is able to hide a malicious --index-url option in a requirements file that a victim installs with pipenv, the attacker can embed arbitrary malicious code in packages served from their malicious index server that will be executed on the victims host during installation (remote code execution/RCE). When pip installs from a source distribution, any code in the setup.py is executed by the install process. This issue is patched in version 2022.1.8. The GitHub Security Advisory contains more information about this vulnerability.

Weakness

The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.

Affected Software

Extended Description

Specified quantities include size, length, frequency, price, rate, number of operations, time, and others. Code may rely on specified quantities to allocate resources, perform calculations, control iteration, etc. When the quantity is not properly validated, then attackers can specify malicious quantities to cause excessive resource allocation, trigger unexpected failures, enable buffer overflows, etc.

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/pypa/pipenv/commit/439782a8ae36c4762c88e43d5f0d8e563371b46f
• https://github.com/pypa/pipenv/releases/tag/v2022.1.8
• https://github.com/pypa/pipenv/security/advisories/GHSA-qc9x-gjcv-465w
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/56HBA3EOSLEDNCCBJVHE6DO34P56EOUM/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KCROBYHUS6DKQPCXBRPCZ5CDBNQTYAWT/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QHQRIWKDP3SVJABAPEXBIQPKDI6UP7G4/