CVE-2018-14072 in libsixel
Summary
by MITRE
libsixel 1.8.1 has a memory leak in sixel_decoder_decode in decoder.c, image_buffer_resize in fromsixel.c, and sixel_decode_raw in fromsixel.c.
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Analysis
by VulDB Data Team • 04/09/2023
The vulnerability identified as CVE-2018-14072 affects libsixel version 1.8.1, a library used for handling sixel graphics format commonly employed in terminal-based image rendering and display applications. This memory leak vulnerability manifests across three critical functions within the library's codebase, specifically in the sixel_decoder_decode function located in decoder.c, the image_buffer_resize function in fromsixel.c, and the sixel_decode_raw function also in fromsixel.c. The issue represents a significant security concern as it allows for unauthorized memory consumption that can lead to system instability and potential denial of service conditions.
The technical flaw stems from improper memory management within the sixel graphics processing functions, where allocated memory blocks are not correctly deallocated or managed during the decoding process. When processing sixel formatted data, the library fails to properly release memory resources that were previously allocated for image buffer operations and decoding activities. This memory leak occurs repeatedly during the processing of malformed or specially crafted sixel input data, causing progressive memory consumption that can eventually exhaust available system resources. The vulnerability is particularly concerning because it affects core decoding functions that are integral to the library's operation, making it difficult to isolate and prevent without comprehensive code-level fixes.
The operational impact of this memory leak vulnerability extends beyond simple resource exhaustion, potentially enabling attackers to perform denial of service attacks against systems utilizing libsixel. When applications that depend on this library process malicious sixel data, the progressive memory consumption can lead to system slowdowns, application crashes, or complete system instability. The vulnerability is particularly dangerous in environments where the library is used in server applications or systems handling untrusted input data, as it can be exploited to consume system resources over time and potentially render services unavailable to legitimate users. The nature of the memory leak suggests that it could be triggered repeatedly through various input scenarios, making it a persistent threat that requires immediate attention.
Mitigation strategies for this vulnerability should focus on immediate patching of the affected libsixel library to version 1.8.2 or later, which contains the necessary memory management fixes. Organizations should also implement input validation measures to filter or sanitize sixel data before processing, particularly when handling untrusted sources. The vulnerability aligns with CWE-401, which describes improper management of dynamic memory allocation, and can be mapped to ATT&CK technique T1499.004, specifically covering resource exhaustion attacks that target memory consumption. System administrators should monitor for unusual memory usage patterns and implement automated alerts to detect potential exploitation attempts. Additionally, deploying network segmentation and access controls can limit the potential impact of successful exploitation attempts, while regular security assessments should verify that no other applications are affected by similar memory management issues in their dependencies.