CVE-2025-15564: Mapnik Divide by Zero DoS Vulnerability

CVE-2025-15564 Overview

A divide by zero vulnerability has been discovered in Mapnik, an open-source toolkit for rendering maps. This vulnerability affects the function mapnik::detail::mod<...>::operator in the file src/value.cpp. The flaw allows an attacker with local access to trigger an unhandled division by zero condition, potentially causing a denial of service condition. The exploit has been publicly disclosed, and while the project maintainers were informed early through an issue report, no response has been received.

Critical Impact

Local attackers can exploit this divide by zero vulnerability to cause application crashes and denial of service conditions in applications utilizing the Mapnik library for map rendering.

Affected Products

• Mapnik up to version 4.2.0
• Applications and services built on affected Mapnik versions
• Systems utilizing Mapnik for map rendering and cartographic operations

Discovery Timeline

• February 7, 2026 - CVE-2025-15564 published to NVD
• February 9, 2026 - Last updated in NVD database

Technical Details for CVE-2025-15564

Vulnerability Analysis

This vulnerability is classified under CWE-369 (Divide By Zero), a numeric error that occurs when an application attempts to divide a number by zero without proper validation. In the context of Mapnik, this flaw exists within the modulo operator implementation in the mapnik::detail::mod<...>::operator function located in src/value.cpp.

The vulnerability requires local access to exploit, meaning an attacker must have the ability to provide crafted input to the affected function. When triggered, the divide by zero condition results in undefined behavior that typically manifests as an application crash, leading to denial of service for any application relying on the Mapnik library.

Root Cause

The root cause of this vulnerability is insufficient input validation in the modulo operator function within src/value.cpp. The mapnik::detail::mod<...>::operator function fails to properly check if the divisor operand is zero before performing the modulo operation. This missing validation allows crafted input to trigger the arithmetic exception.

Attack Vector

The attack vector for this vulnerability is local, requiring an attacker to have the ability to supply malicious input to an application using the affected Mapnik library. Exploitation involves providing a zero value as the divisor in a modulo operation context. While the attack complexity is low and requires no user interaction, the impact is limited to availability through denial of service—there is no direct path to data confidentiality or integrity compromise.

The vulnerability mechanism involves the modulo operator in the value processing logic. When the operator receives a zero divisor without proper validation, the CPU generates a divide-by-zero exception that terminates the application. See GitHub Issue #4545 and the PoC repository for technical details.

Detection Methods for CVE-2025-15564

Indicators of Compromise

• Application crashes with arithmetic exception or SIGFPE signals when processing map data
• Unexpected termination of services utilizing Mapnik for map rendering
• Core dumps or crash logs indicating division by zero in src/value.cpp
• Repeated service restarts in map rendering components

Detection Strategies

• Monitor application logs for SIGFPE (floating-point exception) signals originating from Mapnik-related processes
• Implement crash monitoring for services that utilize Mapnik library functionality
• Review input data for suspicious zero values in contexts where modulo operations may occur
• Deploy static analysis tools to identify similar divide-by-zero conditions in dependent code

Monitoring Recommendations

• Configure process monitoring to alert on repeated crashes of Mapnik-dependent applications
• Enable core dump analysis for early detection of exploitation attempts
• Monitor system stability metrics for services utilizing map rendering functionality
• Implement input validation logging to track potentially malicious input patterns

How to Mitigate CVE-2025-15564

Immediate Actions Required

• Assess exposure by identifying all applications and services utilizing Mapnik versions up to 4.2.0
• Implement input validation at the application layer to filter zero divisor values before they reach Mapnik
• Consider deploying service isolation or containerization to limit the impact of potential crashes
• Monitor the Mapnik GitHub repository for security patches or updates

Patch Information

As of the last modification date, the Mapnik project has not yet responded to the vulnerability report submitted through GitHub Issue #4545. Organizations should monitor the official Mapnik repository for patch releases and apply updates as soon as they become available. Additional technical details are tracked in VulDB #344502.

Workarounds

• Implement application-level input validation to reject zero values in modulo operation contexts
• Deploy process restart automation to minimize downtime from potential crashes
• Use containerization or sandboxing to isolate Mapnik-dependent services and limit crash impact
• Consider rate limiting or access controls to reduce the attack surface for local exploitation

# Example input validation wrapper configuration
# Add validation layer before Mapnik processing
# Ensure divisor values are validated before modulo operations
# Monitor for zero-value inputs in map data processing pipelines