CVE-2017-6962 in apng2gif
Summary
by MITRE
An issue was discovered in apng2gif 1.7. There is an integer overflow resulting in a heap-based buffer overflow. This is related to the read_chunk function making an unchecked addition of 12.
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Analysis
by VulDB Data Team • 09/09/2020
The vulnerability identified as CVE-2017-6962 resides within the apng2gif 1.7 utility, a tool designed to convert animated png files to gif format. This particular flaw represents a critical security issue that stems from improper input validation and arithmetic handling within the software's core processing functions. The vulnerability manifests as an integer overflow condition that ultimately leads to a heap-based buffer overflow, creating potential avenues for arbitrary code execution or system compromise. The issue specifically occurs within the read_chunk function where an unchecked addition operation involving the value twelve triggers the overflow condition.
The technical implementation of this vulnerability involves the manipulation of integer values during the parsing of apng file structures. When the read_chunk function processes incoming data, it performs an arithmetic operation that fails to properly validate the resulting integer value before using it for memory allocation decisions. This unchecked addition of twelve creates a scenario where an attacker can craft malicious input that causes the integer to exceed its maximum representable value, thereby wrapping around to a much smaller value. The resulting overflow condition allows subsequent memory operations to allocate insufficient buffer space, leading to heap corruption when the application attempts to write beyond the allocated boundaries.
From an operational perspective, this vulnerability presents significant risks to systems utilizing apng2gif 1.7 for image conversion tasks. The heap-based buffer overflow creates opportunities for attackers to execute malicious code with the privileges of the affected application, potentially leading to complete system compromise. The vulnerability is particularly concerning because it can be triggered through normal file processing operations, meaning that simply opening or converting a specially crafted apng file could expose systems to attack. This makes the flaw especially dangerous in environments where automated processing or user-uploaded content is common.
The vulnerability aligns with CWE-190, which categorizes integer overflow conditions as a fundamental weakness in software arithmetic handling. It also maps to ATT&CK technique T1059.007, which covers the use of scripting languages to execute malicious code, as the overflow could potentially be exploited through script-based attack vectors. Additionally, this vulnerability demonstrates characteristics of T1203, which involves the exploitation of input validation flaws to achieve unauthorized system access. The heap corruption aspect of this vulnerability also relates to ATT&CK technique T1068, covering the exploitation of system vulnerabilities for privilege escalation.
Mitigation strategies for CVE-2017-6962 should prioritize immediate software updates to versions that address the integer overflow condition within the read_chunk function. Organizations should implement input validation measures that check for potential overflow conditions before arithmetic operations are performed. The fix should involve proper bounds checking on integer values and ensuring that all calculations involving buffer sizes are validated against maximum allowable limits. Additionally, deployment of runtime protections such as address space layout randomization and stack canaries can provide additional defense-in-depth measures. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other image processing utilities and ensure comprehensive protection against heap-based buffer overflow exploits.