CVE-2026-111270 in libmodplug
Summary
by MITRE • 10/16/2026
libmodplug through 0.8.9.1 contains a heap-based out-of-bounds write in CSoundFile::ReadDSM() in src/load_dsm.cpp because nPat is never checked against MAX_PATTERNS. Attackers can supply a crafted DSM file with over 240 PATT chunks or a wrapping patt_len value to corrupt heap memory and crash the consuming process.
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Analysis
by VulDB Data Team • 10/16/2026
The vulnerability identified in libmodplug versions through 0.8.9.1 represents a critical security flaw within the library's module file parsing logic, specifically located in the CSoundFile::ReadDSM() function found in src/load_dsm.cpp. This component is responsible for interpreting and loading Digital Sound Module files, a format historically used to store music data composed using tracker software. The core technical deficiency lies in the absence of bounds checking for the variable nPat, which tracks the number of patterns within the module file. During the parsing process, the application fails to validate whether this count exceeds the predefined constant MAX_PATTERNS, effectively allowing an attacker to manipulate internal memory structures by supplying a maliciously crafted DSM file with over 240 PATT chunks or by exploiting integer wrapping mechanisms in the patt_len value. This lack of validation is a classic example of improper input handling that leads directly to heap-based out-of-bounds write conditions.
From a technical perspective, this vulnerability aligns closely with CWE-787: Out-of-Bounds Write, as it involves writing data beyond the allocated boundaries of a buffer in the heap memory space. The absence of rigorous boundary checks allows an attacker to overwrite adjacent memory structures that are critical for program execution flow or state management. By crafting a DSM file where the number of patterns exceeds the expected limit or by manipulating length fields to cause integer overflow, the attacker can corrupt the heap metadata or arbitrary data segments. This corruption destabilizes the application's memory layout, leading to unpredictable behavior and potential control over instruction pointers if specific memory regions are targeted with shellcode or return-oriented programming gadgets.
The operational impact of this vulnerability is significant for any software that integrates libmodplug as a dependency for audio playback capabilities. An attacker who can trick a user into opening a malicious DSM file can trigger the out-of-bounds write, resulting in immediate application crashes due to memory corruption errors such as segmentation faults or access violations. While the primary observed effect is denial of service through process termination, heap-based vulnerabilities often serve as precursors to more severe exploits. If an attacker successfully controls the overwritten data and has knowledge of the target's memory layout, they may achieve arbitrary code execution with the privileges of the compromised application. This transforms a simple media playback tool into a potential vector for remote code execution attacks, particularly in environments where users are expected to open files from untrusted sources without rigorous sandboxing or validation mechanisms.
To mitigate this risk, developers must implement strict input validation within the CSoundFile::ReadDSM() function before processing pattern data. The immediate fix involves adding explicit checks to ensure that nPat does not exceed MAX_PATTERNS and validating all length fields against expected maximums to prevent integer wrapping issues. Beyond code-level fixes, organizations should adopt defense-in-depth strategies such as enabling heap protection mechanisms like Address Sanitizer during development and deployment of security-hardened binaries in production environments where feasible. Furthermore, integrating static analysis tools that detect out-of-bounds access patterns can help identify similar vulnerabilities across the codebase. From a threat intelligence perspective, this vulnerability maps to MITRE ATT&CK techniques related to initial exploitation via file execution, specifically highlighting how malformed media files are leveraged to compromise system stability and potentially gain unauthorized control over user systems through memory corruption exploits.