CVE-2026-112018 in cgltf
Summary
by MITRE • 10/18/2026
cgltf through 1.15 contains a heap out-of-bounds write vulnerability in cgltf_accessor_unpack_floats() that allows attackers to write outside the output buffer via unchecked sparse accessor indices. Attackers can supply a crafted glTF or GLB file with large sparse indices to corrupt heap memory, crash applications, and potentially execute code when cgltf_validate() is not called.
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Analysis
by VulDB Data Team • 10/18/2026
The vulnerability identified in cgltf versions through 1.15 represents a critical security flaw within the library's handling of glTF asset data, specifically targeting the function responsible for unpacking sparse accessor indices into floating-point arrays. This heap-based out-of-bounds write occurs when the parser processes files that contain sparse accessors with index values exceeding the bounds of the allocated output buffer. The root cause lies in a failure to perform adequate validation checks on these indices before they are used as offsets or array subscripts during memory operations. In standard glTF workflows, it is common practice for developers to call cgltf_validate() prior to processing asset data to ensure structural integrity and safety. However, when this validation step is omitted, the library proceeds directly to parse and unpack the sparse accessor data without verifying that the indices fall within acceptable limits relative to the buffer size allocated by the application or internal mechanisms.
From a technical perspective, the exploitation of this vulnerability relies on crafting a malicious glTF or GLB file where the sparse accessors contain index values significantly larger than expected. When cgltf_accessor_unpack_floats() processes these crafted indices, it calculates memory addresses that lie beyond the end of the heap-allocated buffer intended to hold the unpacked float data. The subsequent write operation corrupts adjacent heap metadata or other critical application structures stored in contiguous memory regions. This type of memory corruption is particularly dangerous because it can lead to arbitrary code execution if an attacker can control the content written outside the bounds, allowing them to overwrite function pointers, exception handlers, or other executable logic within the process address space. Even without achieving remote code execution, the immediate impact includes application crashes and denial of service conditions due to heap corruption triggering segmentation faults or abort signals from memory allocators like glibc's malloc implementation.
The operational impact extends beyond simple stability issues, as this vulnerability affects any software that integrates cgltf for rendering 3D graphics in games, virtual reality applications, web browsers with WebGL support, and digital content creation tools. Attackers can distribute malicious glTF files through phishing campaigns, compromised websites, or shared repositories to trigger the flaw when a victim opens or renders the asset. The absence of mandatory validation calls means that many implementations remain exposed by default unless developers explicitly add security checks. This aligns with CWE-787, which classifies out-of-bounds writes as a fundamental memory safety error often resulting from insufficient boundary checking on array indices. Furthermore, this vulnerability maps to MITRE ATT&CK technique T1203, where exploitation of software vulnerabilities is used for initial access or execution, highlighting the risk posed by unvalidated input in parsing libraries that handle complex binary formats.
Mitigation strategies must focus on both immediate patching and long-term defensive coding practices. The primary remediation is to upgrade cgltf to version 1.16 or later, where this specific bounds-checking logic has been corrected to ensure sparse accessor indices are validated against the buffer size before any write operations occur. For applications unable to update immediately, developers should enforce a strict workflow that mandates calling cgltf_validate() on all loaded assets prior to unpacking accessors. Additionally, integrating fuzz testing into continuous integration pipelines can help detect similar parsing flaws early in development cycles. Security-conscious implementations may also employ memory-safe wrappers or sandboxing techniques to limit the blast radius of potential heap corruptions, ensuring that even if an out-of-bounds write occurs, it does not compromise critical system components or allow privilege escalation.