CVE-2002-0059 in zlib
Summary
by MITRE
The decompression algorithm in zlib 1.1.3 and earlier, as used in many different utilities and packages, causes inflateEnd to release certain memory more than once (a "double free"), which may allow local and remote attackers to execute arbitrary code via a block of malformed compression data.
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Analysis
by VulDB Data Team • 12/26/2024
The vulnerability identified as CVE-2002-0059 represents a critical memory corruption flaw within the zlib compression library version 1.1.3 and earlier implementations. This issue stems from improper handling within the decompression algorithm that leads to a double free condition during memory management operations. The flaw specifically manifests when the inflateEnd function attempts to release memory that has already been freed, creating a scenario where the same memory address is deallocated twice. This fundamental memory management error creates a potential exploitation vector for both local and remote attackers seeking to execute arbitrary code on vulnerable systems.
The technical implementation of this vulnerability involves the zlib library's compression and decompression functions that process compressed data streams. When malformed compression data is processed through the inflateEnd function, the memory management routines fail to properly track memory allocation status, resulting in the same memory block being freed multiple times. This double free condition can corrupt the heap memory structure and potentially allow attackers to manipulate memory pointers or overwrite critical data structures. The vulnerability is particularly dangerous because it can be triggered through various compression formats and protocols that utilize zlib, including http web servers, ftp clients, email clients, and numerous network services that rely on compressed data transmission.
From an operational perspective, this vulnerability poses significant risks to system security and stability across numerous applications and services that depend on zlib for compression functionality. The impact extends beyond simple denial of service scenarios to potentially enable complete system compromise through arbitrary code execution. Attackers can craft specially malformed compressed data streams that trigger the double free condition when processed by vulnerable applications, potentially leading to privilege escalation, data theft, or complete system takeover. The widespread adoption of zlib across various software platforms means that exploitation can affect a broad range of systems including web servers, network devices, and application software that utilize compression features.
The vulnerability aligns with CWE-415, which describes improper deallocation of memory, and more specifically with CWE-416, concerning the use of freed memory. Additionally, this issue maps to ATT&CK technique T1059, which involves executing malicious code through command and scripting interpreters, as attackers could leverage the arbitrary code execution capability to deploy additional malicious payloads. The double free condition creates a memory corruption scenario that can be exploited through various attack vectors, including network-based attacks that send malformed compressed data to vulnerable services or local attacks that manipulate compressed files. Organizations should prioritize immediate remediation through zlib library updates to version 1.1.4 or later, which contains the necessary fixes for proper memory management during decompression operations.
Mitigation strategies should include immediate patching of all systems running vulnerable zlib versions, comprehensive vulnerability scanning to identify affected applications and services, and implementation of network monitoring to detect attempts to exploit this vulnerability through malformed compressed data. Security teams should also consider implementing application whitelisting controls and restricting access to services that process compressed data from untrusted sources. The remediation process requires careful testing to ensure that patching does not introduce compatibility issues with existing applications that rely on zlib functionality, while also verifying that all instances of the vulnerable library have been properly updated across the entire infrastructure.