CVE-2023-45805

Malicious pdm.lock file allows project substitution

• CVSS 7.8
• CWE-20 Improper Input Validation
• Input Validation and Sanitization
• Remote

pdm is a Python package and dependency manager supporting the latest PEP standards. It's possible to craft a malicious `pdm.lock` file that could allow e.g. an insider or a malicious open source project to appear to depend on a trusted PyPI project, but actually install another project. A project `foo` can be targeted by creating the project `foo-2` and uploading the file `foo-2-2.tar.gz` to pypi.org. PyPI will see this as project `foo-2` version `2`, while PDM will see this as project `foo` version `2-2`. The version must only be `parseable as a version` and the filename must be a prefix of the project name, but it's not verified to match the version being installed. Version `2-2` is also not a valid normalized version per PEP 440. Matching the project name exactly (not just prefix) would fix the issue. When installing dependencies with PDM, what's actually installed could differ from what's listed in `pyproject.toml` (including arbitrary code execution on install). It could also be used for downgrade attacks by only changing the version. This issue has been addressed in commit `6853e2642df` which is included in release version `2.9.4`. Users are advised to upgrade. There are no known workarounds for this vulnerability.

CVE

CVE-2023-45805

CWE

CWE-20 Improper Input Validation

CVSS base score

7.8

Published

2023-10-20

OWASP

A06 Vulnerable and Outdated Components

Orthogonal defect classification

Function

Code defect classification

Incorrect Functionality

Category

Input Validation and Sanitization

Subcategory

Insecure Parsing or Deserialization

Accessibility scope

Remote

Impact

Arbitrary Code Execution

Fixed by upgrading

Yes

Solution

Update PDM to version 2.9.4 or higher.

def calculate(expression):
    """Calculate expression - VULNERABLE to code injection"""
    # VULNERABILITY: eval() executes arbitrary Python code
    return eval(expression)

# Example exploitation:
# calculate("__import__('os').system('whoami')")

import ast
import operator

def calculate_secure(expression):
    """Securely calculate mathematical expression"""
    try:
        # Parse expression into AST
        tree = ast.parse(expression, mode='eval')
        return eval_ast_node(tree.body)
    except:
        return None

def eval_ast_node(node):
    """Safely evaluate AST node"""
    if isinstance(node, ast.Constant):
        return node.value
    elif isinstance(node, ast.BinOp):
        left = eval_ast_node(node.left)
        right = eval_ast_node(node.right)
        ops = {ast.Add: operator.add, ast.Sub: operator.sub}
        return ops[type(node.op)](left, right)
    else:
        raise ValueError("Unsupported operation")

@misc{vaitp:cve202345805,
  title        = {{Malicious pdm.lock file allows project substitution}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2023},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2023-45805},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2023-45805/}}
}