CVE-2026-102729 in GUIX
Summary
by MITRE • 09/29/2026
`gx_binres_theme_load()` sizes its theme buffer for the theme it was asked for, and allocates it even when the resource holds no theme with that id. A theme id at or past the theme count declared by the resource gets a buffer of zero bytes. The load pass then walks past the end of the theme table, takes whatever follows as a theme header, and writes a `GX_THEME` and its tables into that zero-byte buffer.
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Analysis
by VulDB Data Team • 09/29/2026
The vulnerability described involves an out-of-bounds write condition within the gx_binres_theme_load function, which is responsible for loading graphical user interface themes from binary resources. The core technical flaw stems from insufficient validation of resource identifiers against declared bounds. Specifically, when a caller requests a theme using an identifier that equals or exceeds the total number of themes defined in the resource file, the system incorrectly allocates a buffer with zero bytes rather than rejecting the request or handling it as an error condition. This logic error creates a scenario where subsequent memory operations proceed without adequate spatial constraints, leading to critical security implications.
Following the allocation of this zero-byte buffer, the execution flow proceeds to parse and write data into the allocated space. The function walks past the end of the valid theme table structure and interprets arbitrary adjacent memory contents as a valid theme header. It then attempts to write a GX_THEME structure along with its associated tables directly into the undersized or non-existent buffer. This action constitutes an out-of-bounds write, allowing data from outside the intended resource boundary to be written into system memory. Depending on the specific implementation details and surrounding memory layout, this can result in heap corruption, stack overflow, or arbitrary code execution if attacker-controlled input influences the theme ID selection process.
From a classification perspective, this vulnerability aligns with CWE-787: Out-of-bounds Write, as it involves writing data beyond the allocated buffer boundary due to improper size calculation and bounds checking. Additionally, because the flaw allows for potential memory corruption that could be leveraged to execute arbitrary code or disrupt service availability, it relates closely to CWE-120: Buffer Overflow. In terms of attack vectors, this type of vulnerability is often exploited through input manipulation where an adversary provides a maliciously crafted theme ID to trigger the out-of-bounds write condition. This maps to ATT&CK technique T1190: Exploit Public-Facing Application if the resource loading mechanism is exposed via network services or user-facing interfaces, allowing remote exploitation without prior authentication.
The operational impact of this vulnerability can be severe. In embedded systems or applications relying on binary resources for UI rendering, exploiting this flaw could lead to application crashes, denial of service, or more critically, privilege escalation and full system compromise if the corrupted memory contains sensitive control flow data such as return addresses or function pointers. Attackers might leverage heap spraying techniques combined with precise offset calculations to gain code execution capabilities. The lack of proper boundary checks means that even seemingly innocuous resource loading functions can become vectors for sophisticated attacks targeting memory integrity.
Mitigation strategies should focus on implementing strict input validation and bounds checking before any buffer allocation or data parsing occurs. Developers must verify that the requested theme ID is strictly less than the declared count of themes in the binary resource file. If an invalid identifier is detected, the function should return an error code immediately rather than proceeding with memory operations. Furthermore, employing static analysis tools during development and dynamic fuzzing testing can help identify such off-by-one or out-of-bounds errors early in the lifecycle. Using safer memory allocation functions that enforce size limits and integrating Address Sanitizer (ASan) into the build process for debugging purposes are also recommended practices to detect these vulnerabilities before deployment.