CVE-2026-111271 in libmodplug
Summary
by MITRE • 10/16/2026
libmodplug through 0.8.9.1 contains a heap-based out-of-bounds read vulnerability in CSoundFile::ReadAMS2() in src/load_ams.cpp that allows attackers to read adjacent heap memory via crafted AMS files. Attackers can supply an AMS module whose pattern effect bytes keep bit 7 set, driving the decoder past the input buffer and crashing any libmodplug consumer.
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Analysis
by VulDB Data Team • 10/16/2026
The vulnerability identified within libmodplug versions up through 0.8.9.1 represents a critical heap-based out-of-bounds read flaw located specifically in the CSoundFile::ReadAMS2 function found in the src/load_ams.cpp source file. This component is responsible for parsing and decoding Advanced Module System files, a format widely used in tracker music creation. The core technical deficiency arises from insufficient validation of pattern effect bytes during the processing of AMS modules. Specifically, when an attacker supplies a crafted AMS module where specific pattern effect bytes maintain bit 7 set, it triggers an incorrect execution path within the decoder logic. This condition causes the internal pointer or index used to traverse the input buffer to advance beyond its allocated boundaries without proper bounds checking mechanisms in place to halt the operation.
From a technical perspective, this flaw allows attackers to read adjacent heap memory that lies immediately following the intended input buffer. In many scenarios involving out-of-bounds reads, particularly those affecting audio decoders or media processing libraries, such access can lead to information disclosure if the adjacent memory contains sensitive data such as cryptographic keys, session tokens, or other private user information. However, in this specific instance, the primary operational impact observed is a denial of service condition. The out-of-bounds read drives the decoder into an invalid state that inevitably results in a crash for any application consuming libmodplug to process these maliciously crafted files. This stability issue disrupts availability and can be exploited to cause resource exhaustion or application termination without requiring further exploitation steps like code execution, although the memory access itself remains a significant security concern under broader threat models.
This vulnerability aligns with Common Weakness Enumeration CWE-125, which describes Out-of-bounds Read vulnerabilities where software reads data past the end of a buffer. It also relates to CWE-20, Improper Input Validation, as the root cause is the failure to adequately verify that input data conforms to expected structural constraints before processing. In terms of adversary tactics and techniques, this flaw can be leveraged within MITRE ATT&CK framework contexts related to Initial Access via Spearphishing Attachment or Drive-by Compromise if an attacker can trick a user into opening a malicious AMS file in a vulnerable media player or audio editing software. The exploitation vector is typically remote when the library is integrated into network-facing services, but more commonly local through social engineering tactics targeting end-users of music production tools.
Mitigation strategies for this vulnerability primarily involve updating libmodplug to a patched version that addresses the bounds checking logic within the ReadAMS2 function. Developers integrating this library should ensure they are using versions released after the fix was applied and validated by the maintainers. For organizations unable to immediately update, implementing strict input validation at the application layer before passing AMS files to the decoder can provide an additional layer of defense. This includes verifying file headers and structure against known valid formats or sandboxing the decoding process in a restricted environment with limited memory access privileges. Security teams should also monitor for any indicators of compromise related to unusual crashes in applications utilizing libmodplug, as these may signal attempted exploitation by automated scanners targeting this specific weakness.