CVE-2009-2624 in gzip
Summary
by MITRE
The huft_build function in inflate.c in gzip before 1.3.13 creates a hufts (aka huffman) table that is too small, which allows remote attackers to cause a denial of service (application crash or infinite loop) or possibly execute arbitrary code via a crafted archive. NOTE: this issue is caused by a CVE-2006-4334 regression.
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Analysis
by VulDB Data Team • 04/29/2026
The vulnerability identified as CVE-2009-2624 represents a critical flaw in the gzip compression utility that affects versions prior to 1.3.13. This issue stems from a regression introduced by CVE-2006-4334, which fundamentally altered the Huffman table construction process within the inflate.c source file. The flaw manifests in the huft_build function where the Huffman tables are constructed during decompression operations, creating tables that are insufficiently sized to handle certain malformed input data.
The technical implementation of this vulnerability involves the improper calculation and allocation of memory for Huffman decoding tables during the decompression phase of gzip archives. When processing specially crafted archive files, the huft_build function fails to allocate adequate table space, leading to memory corruption conditions that can result in either application crashes or infinite looping behavior. This memory management error occurs because the function does not properly account for the maximum possible size requirements of Huffman tables when dealing with compressed data that contains malformed or maliciously constructed Huffman codes.
From an operational perspective, this vulnerability presents significant risks to systems that process untrusted archive files, particularly those that rely on gzip decompression for automated processing or user-uploaded content. Attackers can exploit this weakness by creating malicious archive files that, when decompressed, trigger the insufficient table allocation, causing denial of service conditions that can render systems unavailable or potentially allowing for arbitrary code execution. The impact extends beyond simple service disruption as the vulnerability can be leveraged in automated attacks against web applications, file servers, or any system that accepts and processes gzip-compressed data without proper validation.
The vulnerability aligns with CWE-129, which addresses issues related to insufficient size checks in buffer management, and demonstrates characteristics consistent with CWE-121, concerning buffer overflow conditions in heap-based memory allocation. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and potentially T1059, covering execution through command-line interfaces when systems process compromised archives. The root cause analysis reveals that this issue is fundamentally a memory allocation problem that could be addressed through proper bounds checking and validation of Huffman table size calculations. The recommended mitigation strategy involves upgrading to gzip version 1.3.13 or later, which contains the necessary patches to properly handle Huffman table allocation. Additionally, system administrators should implement input validation measures that reject suspicious archive files and consider deploying intrusion detection systems that can identify attempts to exploit this vulnerability through malformed gzip data. Organizations should also review their decompression workflows to ensure that untrusted data is processed in isolated environments that can contain potential exploitation attempts.