CVE-2026-111136 in libinstpatch
Summary
by MITRE • 10/15/2026
libInstPatch through 1.1.7 contains a heap out-of-bounds write vulnerability in the SoundFont 2 loader because ipatch_sf2_gen_is_valid() does not range-check generator IDs before the validity mask test. Attackers can supply crafted SF2 files with out-of-range pgen or igen generator IDs to write attacker-chosen values past the zone genarray, corrupting heap memory and crashing Swami or other consumers.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified in libInstPatch versions through 1.1.7 represents a critical heap-based buffer overflow within the SoundFont 2 loader component. This flaw stems from an insufficient validation mechanism when processing generator identifiers, specifically within the ipatch_sf2_gen_is_valid function. The core technical deficiency lies in the order of operations during data validation; the software fails to perform range-checking on generator IDs before applying a validity mask test. In standard secure coding practices for parsing structured binary formats like SoundFont 2 files, input values must be strictly bounded against known array limits prior to any further processing or memory access attempts. By omitting this preliminary check, the application allows malformed data structures containing out-of-range pgen (parent generator) and igen (instance generator) identifiers to bypass initial security filters.
When an attacker supplies a crafted SoundFont 2 file with these invalid generator IDs, the library proceeds to interpret them as valid indices for memory access operations. Consequently, this leads to a heap out-of-bounds write condition where the application attempts to write data at memory addresses located beyond the allocated zone genarray boundary. This improper memory manipulation results in the corruption of adjacent heap structures and metadata. The immediate operational impact is typically observed as an application crash or segmentation fault in consumers such as Swami, which relies on libInstPatch for audio sample management. However, given that this involves arbitrary write capabilities within the heap context, the potential for more severe exploitation exists beyond simple denial-of-service scenarios.
From a threat modeling perspective, this vulnerability aligns with CWE-787: Out-of-bounds Write and CWE-20: Improper Input Validation. The lack of boundary checking on user-controlled input directly facilitates memory corruption that can potentially be leveraged for code execution if the attacker can control the data written to the out-of-bounds location and manipulate heap metadata accordingly. In terms of adversary tactics, this falls under ATT&CK technique T1203: Exploitation for Client Execution, as it targets client-side audio processing software through maliciously crafted media files designed to trigger execution flow during parsing routines.
To mitigate this vulnerability, developers must enforce strict input validation at the earliest possible stage of data ingestion. Specifically, the ipatch_sf2_gen_is_valid function should be updated to verify that generator IDs fall within the acceptable range defined by the SoundFont 2 specification before any mask-based validity checks are performed. Additionally, implementing bounds checking on all array accesses derived from external file inputs is essential to prevent heap corruption. For end-users and system administrators, immediate mitigation involves updating libInstPatch to a patched version where this validation logic has been corrected. Until an update is available, restricting the execution of untrusted audio files or using sandboxed environments can reduce the risk of exploitation by limiting the potential impact of memory corruption events on the host system.