CVE-2025-70887: Signify Privilege Escalation Vulnerability

CVE-2025-70887 Overview

A privilege escalation vulnerability exists in ralphje Signify before version 0.9.2. The vulnerability is located in the signed_data.py and context.py components, allowing a remote attacker to escalate privileges within affected systems. Signify is a Python library used for verifying Authenticode signatures on Windows executables, making this vulnerability particularly concerning for environments that rely on code signature verification as part of their security infrastructure.

Critical Impact

Remote attackers can exploit flaws in the signature verification components to escalate privileges, potentially bypassing security controls that rely on Authenticode signature validation.

Affected Products

• ralphje Signify versions prior to 0.9.2
• Applications and systems using vulnerable versions of the Signify library for Authenticode verification

Discovery Timeline

• 2026-03-25 - CVE CVE-2025-70887 published to NVD
• 2026-03-26 - Last updated in NVD database

Technical Details for CVE-2025-70887

Vulnerability Analysis

The vulnerability affects the core signature verification functionality within the Signify library. The signed_data.py component handles the parsing and validation of signed data structures, while context.py manages the verification context. Flaws in these components allow attackers to manipulate the signature verification process, potentially leading to privilege escalation.

The issue is related to how the library processes and validates Authenticode signatures, which are commonly used to verify the integrity and authenticity of Windows executables and drivers. When exploited, an attacker could potentially craft malicious payloads that bypass signature verification checks, leading to the execution of untrusted code with elevated privileges.

Root Cause

The root cause stems from improper validation logic within the signed_data.py and context.py modules. The signature verification process does not adequately validate certain edge cases or malformed signature structures, creating an opportunity for attackers to exploit these weaknesses. The fix implemented in commit 64f21c0 addresses these validation gaps in the affected components.

Attack Vector

An attacker can exploit this vulnerability remotely by providing specially crafted signed data to an application using the vulnerable Signify library. The attack does not require authentication and can be triggered when the target application processes malicious input designed to exploit the validation flaws in the signature verification logic.

The exploitation path involves manipulating signature data structures to bypass verification checks, potentially allowing unsigned or maliciously signed code to be accepted as legitimate. This could enable privilege escalation if the affected application operates with elevated permissions or makes trust decisions based on signature verification results.

Detection Methods for CVE-2025-70887

Indicators of Compromise

• Unusual signature verification failures or anomalies in applications using Signify
• Unexpected execution of unsigned or improperly signed executables
• Log entries indicating signature validation bypass attempts
• Modified or tampered Signify library files in Python environments

Detection Strategies

• Monitor applications using Signify for unexpected signature verification behaviors
• Implement integrity monitoring for Python package installations to detect unauthorized modifications
• Review application logs for signature verification anomalies or unexpected validation results
• Deploy network monitoring to detect potential exploitation attempts targeting signature verification endpoints

Monitoring Recommendations

• Audit Python environments for vulnerable versions of the Signify library (< 0.9.2)
• Enable verbose logging in applications performing Authenticode verification
• Monitor for privilege escalation events following signature verification operations
• Implement alerting for failed signature verifications that subsequently result in code execution

How to Mitigate CVE-2025-70887

Immediate Actions Required

• Upgrade Signify to version 0.9.2 or later immediately
• Review and audit systems using vulnerable versions of the library
• Implement additional signature verification controls as a defense-in-depth measure
• Monitor affected systems for signs of compromise until patching is complete

Patch Information

The vulnerability has been addressed in Signify version 0.9.2. The fix was implemented in GitHub commit 64f21c0, which corrects the validation logic in the signed_data.py and context.py components. Organizations should update to the patched version as soon as possible.

Additional context regarding this issue can be found in GitHub Issue #60. Related issues in the osslsigncode project are documented in GitHub Issue #475, Pull Request #477, and Release v2.11.

Workarounds

• Implement additional signature validation checks at the application level before trusting verification results
• Restrict network access to systems using vulnerable Signify versions to limit remote exploitation risk
• Consider temporarily disabling Signify-based verification and using alternative signature verification methods until patching is complete
• Apply strict input validation for any data processed by the Signify library

# Upgrade Signify to the patched version
pip install --upgrade signify>=0.9.2

# Verify the installed version
pip show signify | grep Version