CVE-2026-75818 in Aspell
Summary
by MITRE • 10/06/2026
GNU Aspell prezip-bin contains a heap-based buffer overflow vulnerability in the decompressor in prog/prezip.c. The decompressor does not properly check buffer space, so a crafted compressed file can cause out-of-bounds read and write operations on the heap. An attacker who convinces a user to process a malicious compressed file with prezip-bin can trigger memory corruption, leading to a processs crash.
This issue was fixed in commit 15b188437f9e0192d4ac4472ad66a4e2f62a782f which will be released in version 0.60.8.3.
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Analysis
by VulDB Data Team • 10/06/2026
The vulnerability identified within GNU Aspell's prezip-bin utility represents a critical heap-based buffer overflow located specifically within the decompressor component of prog/prezip.c. This flaw stems from an insufficient validation mechanism where the software fails to adequately check available buffer space prior to performing memory operations during the decompression process. Consequently, when processing specially crafted compressed files designed to exploit this logic gap, the application performs out-of-bounds read and write operations on the heap. Such memory corruption is particularly dangerous as it allows for arbitrary code execution potential or severe service disruption depending on how the overwritten data interacts with adjacent memory structures.
From a technical perspective, this issue aligns closely with Common Weakness Enumeration CWE-120, which classifies buffer copies without checking size limits, and more specifically CWE-787, denoting out-of-bounds write vulnerabilities that occur in heap memory regions. The absence of proper bounds checking means that an attacker can manipulate the internal state of the application by writing data beyond the allocated boundaries of a heap buffer. This type of exploitation is often leveraged to overwrite function pointers or object metadata stored on the heap, potentially leading to control flow hijacking. In many modern systems with memory protection mechanisms like ASLR and DEP, such vulnerabilities may still result in denial-of-service conditions through segmentation faults if full code execution cannot be achieved immediately.
The operational impact of this vulnerability is primarily centered around local exploitation scenarios where an attacker must convince a user or system administrator to process a maliciously constructed compressed file using the prezip-bin tool. While GNU Aspell itself is a spell-checking library, its associated command-line utilities like prezip-bin are often used in automated pipelines for text processing and compression tasks. If these tools are integrated into build systems, document conversion workflows, or email filtering services without proper sandboxing, an attacker could trigger the vulnerability remotely if they can inject malicious files into those streams. The immediate consequence of triggering this flaw is process crash due to memory corruption, which results in a denial-of-service condition for any service relying on these utilities.
Mitigation strategies should focus on both technical remediation and operational controls. The primary fix involves upgrading GNU Aspell to version 0.60.8.3 or later, where the issue was resolved via commit 15b188437f9e0192d4ac4472ad66a4e2f62a782f. This update includes proper boundary checks within the decompressor logic to ensure that buffer operations remain within allocated limits. For environments where immediate upgrading is not feasible, administrators should restrict access to prezip-bin and implement strict input validation at higher-level application layers before passing compressed data to this utility. Additionally, deploying runtime protection mechanisms such as stack canaries or heap hardening features in the operating system kernel can help mitigate the impact of memory corruption attempts by detecting invalid memory accesses early.
In terms of threat modeling, this vulnerability falls under MITRE ATT&CK technique T1203, which covers exploitation for client-side execution if triggered via user interaction, or potentially T1496 if used in resource hijacking scenarios through denial-of-service effects. Security teams should monitor for unusual memory usage patterns associated with prezip-bin processes and ensure that all third-party dependencies are kept up to date to prevent similar heap-based vulnerabilities from being exploited in adjacent components of the software supply chain.