CVE-2017-6191 in APNGDis
Summary
by MITRE
Buffer overflow in APNGDis 2.8 and below allows a remote attacker to execute arbitrary code via a crafted filename.
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Analysis
by VulDB Data Team • 02/02/2025
The vulnerability identified as CVE-2017-6191 represents a critical buffer overflow flaw within APNGDis version 2.8 and earlier, a tool designed for processing animated portable network graphics files. This vulnerability specifically manifests when the application processes a specially crafted filename that exceeds the allocated buffer space, creating an exploitable condition that can be leveraged by remote attackers. The flaw resides in the application's insufficient input validation mechanisms, particularly in how it handles filename strings during the parsing process. When an attacker submits a maliciously formatted filename, the application fails to properly bounds-check the input data, leading to memory corruption that can be exploited to gain unauthorized code execution privileges. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, where insufficient boundary checking allows an attacker to overwrite adjacent memory locations. The attack vector is particularly concerning as it operates remotely, meaning an adversary can trigger the vulnerability without requiring local system access, making it an attractive target for widespread exploitation. The impact extends beyond simple code execution, as successful exploitation could allow attackers to gain complete control over the affected system, potentially leading to data breaches, system compromise, or further lateral movement within network environments. This vulnerability directly aligns with ATT&CK technique T1203, which describes exploitation for execution through the manipulation of input validation controls. The root cause stems from poor software engineering practices in memory management, where developers failed to implement proper input sanitization and buffer size validation routines. The vulnerability is particularly dangerous in environments where APNGDis is used to process untrusted file inputs, such as web applications, email systems, or file sharing platforms that might encounter maliciously crafted animated png files.
The technical implementation of this buffer overflow exploit relies on the application's handling of filename strings in memory, where the software allocates a fixed-size buffer to store the filename but does not verify that incoming data respects the allocated boundaries. When a crafted filename exceeds the buffer capacity, it overflows into adjacent memory regions, potentially corrupting critical program data structures or executable code. This memory corruption can be manipulated to redirect program execution flow, allowing an attacker to inject and execute arbitrary code within the context of the vulnerable application. The vulnerability's exploitability is enhanced by the fact that APNGDis likely runs with elevated privileges or has access to sensitive system resources, amplifying the potential damage from successful exploitation. The buffer overflow condition creates a predictable memory layout where attackers can precisely overwrite return addresses or function pointers, enabling them to control the execution flow of the program. This type of vulnerability is classified as a stack-based buffer overflow, which is particularly dangerous because it allows attackers to overwrite the stack frame of the calling function, potentially leading to complete system compromise. The attack scenario typically involves an attacker sending a specially crafted filename through a network interface or file processing mechanism that ultimately feeds into the vulnerable APNGDis application. The exploit requires careful crafting of the malicious filename to ensure proper memory layout and execution control, making it a sophisticated attack vector that demonstrates the importance of robust input validation.
The operational impact of CVE-2017-6191 extends far beyond immediate code execution capabilities, as it represents a significant security weakness that can be leveraged for broader system compromise. Organizations that rely on APNGDis for image processing workflows face potential data loss, unauthorized access, and system instability when this vulnerability is exploited. The remote nature of the attack means that adversaries can target systems without physical access, making detection and prevention more challenging. This vulnerability can be particularly devastating in web applications or content management systems that process user-uploaded animated png files, as it creates an attack surface that can be exploited by malicious users. The exploit's potential for privilege escalation makes it especially dangerous in enterprise environments where the application might run with administrative privileges or have access to sensitive data repositories. Security researchers have identified that this vulnerability can be combined with other exploitation techniques to create more sophisticated attacks, such as using the buffer overflow to establish a persistent backdoor or to escalate privileges within the compromised system. The vulnerability's classification as a remote code execution flaw places it in the highest risk category according to industry security frameworks, as it can be exploited without requiring user interaction or local system access. Organizations may experience service disruption, data breaches, or complete system compromise if this vulnerability is not addressed through timely patching or mitigation strategies. The attack can be automated and scaled across multiple systems, making it a preferred target for automated exploitation tools and malware distribution mechanisms.
Mitigation strategies for CVE-2017-6191 must address both immediate remediation and long-term security improvements to prevent similar vulnerabilities from emerging in the future. The most effective immediate solution involves upgrading to APNGDis version 2.9 or later, where the buffer overflow vulnerability has been patched through proper input validation and memory management improvements. Organizations should implement network segmentation and access controls to limit exposure of systems running vulnerable versions of the application, reducing the potential attack surface. Input validation should be strengthened at all levels of the application stack, including filename sanitization and size checking before processing any external input. Security monitoring should be enhanced to detect unusual filename patterns or attempts to exploit buffer overflow conditions, particularly in systems that process user-uploaded content. The implementation of address space layout randomization and stack canaries can provide additional protection against exploitation attempts, though these are not substitutes for proper code-level fixes. Organizations should also consider implementing application whitelisting policies that restrict execution of untrusted applications or files that might trigger the vulnerability. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in other applications within the system. The vulnerability highlights the importance of following secure coding practices and adhering to industry standards such as the OWASP Top Ten and NIST cybersecurity guidelines for preventing buffer overflow conditions. Additionally, developers should implement defensive programming techniques including bounds checking, memory safety validations, and proper error handling to prevent similar issues from occurring in future software releases. System hardening measures such as disabling unnecessary features, restricting file processing capabilities, and implementing proper logging and alerting mechanisms can further reduce the risk of exploitation. The vulnerability serves as a reminder that even seemingly benign applications can present significant security risks when proper input validation and memory management practices are not implemented.