Supply chain · pip · High

Malicious 'pymem-win' package in PyPI executes remote code during import

Threat Engine Auto-Feed · data current as of 2026-09-11

A malicious version (1.14.0) of the 'pymem-win' package in the PyPI ecosystem downloads and executes a remote executable during import. This supply-chain attack poses a critical risk to systems that installed the affected version, potentially leading to arbitrary code execution and system compromise.

  • Package: pip / pymem-win
  • Affected versions: = 1.14.0
  • Severity: critical
  • Reach: ~158/wk
  • Exposure: 70/100 (High)

What happened — Malicious package

The 'pymem-win' package, specifically version 1.14.0, was found to contain malicious obfuscated code. Upon import, this code attempts to download and execute an external executable from a remote server. The repository used for hosting this executable has been linked to previous malicious campaigns.

How the attack works

This is a malicious package attack where a seemingly legitimate software component is compromised to include harmful functionality. When the affected package is integrated into a project and imported, its hidden code triggers an outbound connection to fetch and run an additional payload. This allows an attacker to execute arbitrary code on the compromised system without direct user interaction beyond the package's initial import.

Who's exposed

Profiles most at risk

  • Development teams using the PyPI ecosystem
  • CI/CD pipelines that pull dependencies from PyPI
  • Any system or application that has installed 'pymem-win' version 1.14.0

Conditions that increase exposure

  • Unpinned dependencies that allow fetching the latest or specific vulnerable versions
  • Lack of dependency lockfiles (e.g., requirements.txt with exact versions)
  • Use of internal package mirrors that may not filter malicious packages
  • Automated builds that do not vet new package versions

Blast-radius scenarios

  • If the package is installed and imported, an attacker can achieve remote code execution on the host system.
  • Compromised systems could be used for further network penetration, data exfiltration, or resource abuse.
  • The blast radius extends to any environment where the vulnerable version of 'pymem-win' is executed, including development, testing, and production systems.

What to do (defensive)

Detect

  • Scan dependency trees for 'pymem-win' version 1.14.0.
  • Monitor network traffic for suspicious outbound connections from build systems or applications that use PyPI packages.
  • Review package integrity and provenance using tools that check against known malicious package databases.
  • Implement software composition analysis (SCA) tools to identify vulnerable or malicious dependencies.

Contain

  • Immediately quarantine or isolate any systems identified as having installed 'pymem-win' version 1.14.0.
  • Block network access to known malicious domains or IP addresses associated with the campaign.
  • Prevent further installations of 'pymem-win' version 1.14.0 across all environments.

Remediate

  • Remove 'pymem-win' version 1.14.0 from all affected projects and environments.
  • Replace the package with a known safe version if available, or an alternative if the package is no longer trustworthy.
  • Force-update all dependencies to known good versions and ensure dependency lockfiles are used and committed.
  • Conduct a thorough forensic analysis of any compromised systems to identify the extent of the breach and remove any persistent threats.

Frontier verdict — High

Prioritize immediate detection and removal of 'pymem-win' version 1.14.0 due to critical remote code execution risk during import.

Sources

For detection-engineering and awareness only · point-in-time · not security advice · sourced from the GitHub Advisory Database.