CVE-2026-66759 in Red Hat
Summary
by MITRE • 07/27/2026
A flaw was found in the file-icns plugin in GIMP. When applying a decompressed mask during ICNS image processing, the plugin reads from the mask data buffer without verifying if the cursor exceeds the allocated resource size. If a crafted file contains a truncated mask resource, the icns_decompress function continues reading past the bounds of the buffer. This out-of-bounds read vulnerability results in information disclosure of heap contents, where memory contents are leaked as alpha channel pixel values, or a crash leading to a denial of service if unmapped memory is accessed.
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Analysis
by VulDB Data Team • 07/27/2026
This vulnerability resides within the file-icns plugin of the GNU Image Manipulation Program GIMP, representing a critical out-of-bounds read flaw that can be exploited through maliciously crafted ICNS image files. The issue manifests when the plugin processes decompressed mask data during ICNS image handling operations, specifically in the icns_decompress function where buffer boundary checks are absent. The vulnerability stems from insufficient input validation mechanisms that fail to verify whether cursor positions within the mask data buffer exceed allocated resource limits, creating a scenario where arbitrary memory access can occur.
The technical exploitation of this flaw occurs when GIMP encounters an ICNS file containing a truncated mask resource, causing the icns_decompress function to continue reading beyond the confines of the allocated buffer space. This unbounded read operation can result in two primary security outcomes depending on memory mapping conditions. In cases where accessed memory regions are mapped, the vulnerability leads to information disclosure by leaking heap contents which manifest as alpha channel pixel values in the processed image output. When unmapped memory regions are accessed during the out-of-bounds read, the application experiences a crash resulting in denial of service.
From a cybersecurity perspective, this vulnerability represents a classic buffer overflow condition that aligns with CWE-125, which describes out-of-bounds read vulnerabilities in software systems. The flaw demonstrates characteristics consistent with ATT&CK technique T1059.007 for command and scripting interpreter usage in file processing contexts, as the vulnerability is triggered during normal file handling operations rather than through direct system interaction. The security impact extends beyond simple information disclosure to include potential system stability compromise through denial of service attacks that could target GIMP users or applications utilizing the plugin.
The operational implications of this vulnerability are significant for users who process untrusted image files, as it creates an attack surface where malicious actors can craft ICNS files designed to exploit this behavior. The vulnerability affects any system running GIMP with the file-icns plugin enabled, making it particularly concerning for environments where users frequently process external image content or where GIMP is used in automated workflows. Organizations relying on GIMP for image processing tasks should consider immediate mitigation strategies, as the vulnerability can be exploited through simple file manipulation without requiring elevated privileges or complex attack vectors.
Mitigation approaches should include updating to patched versions of GIMP that address the buffer boundary checking deficiencies in the file-icns plugin, implementing restrictive file validation measures for incoming ICNS content, and deploying network-based intrusion detection systems capable of identifying suspicious file processing patterns. Additionally, system administrators should consider running GIMP instances with restricted privileges and implementing memory protection mechanisms such as address space layout randomization to limit potential exploitation success. The vulnerability highlights the importance of robust input validation in multimedia processing libraries and underscores the need for comprehensive security testing of file format handlers within image manipulation software.