CVE-2021-39595 in SWFTools
Summary
by MITRE • 09/20/2021
An issue was discovered in swftools through 20200710. A stack-buffer-overflow exists in the function rfx_alloc() located in mem.c. It allows an attacker to cause code Execution.
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Analysis
by VulDB Data Team • 09/29/2021
The vulnerability identified as CVE-2021-39595 represents a critical stack buffer overflow flaw within the swftools software suite, specifically affecting versions through 20200710. This issue resides within the rfx_alloc() function located in the mem.c source file, creating a significant security risk that could be exploited by malicious actors to execute arbitrary code on affected systems. The flaw demonstrates characteristics consistent with CWE-121 Stack-based Buffer Overflow, where insufficient bounds checking allows data to overwrite adjacent memory locations on the program stack.
The technical implementation of this vulnerability stems from inadequate input validation and memory management practices within the rfx_alloc() function. When processing certain input data streams, particularly those related to flash file format parsing, the function fails to properly verify buffer boundaries before performing memory allocation operations. This oversight enables attackers to craft malicious input that exceeds the allocated stack buffer size, causing a buffer overflow condition that can be leveraged to overwrite return addresses and execute attacker-controlled code. The vulnerability operates at the kernel level of memory management, making it particularly dangerous as it can bypass standard security mechanisms and potentially escalate privileges.
The operational impact of CVE-2021-39595 extends beyond simple denial of service scenarios, as it provides a pathway for remote code execution attacks that could compromise entire systems. Organizations utilizing swftools for flash file processing, conversion, or manipulation operations face significant risk exposure, particularly in environments where the software processes untrusted input from external sources. Attackers could exploit this vulnerability through various vectors including web applications that utilize swftools for file processing, email attachments, or file upload functionalities. The attack surface is further expanded when considering that many web applications and content management systems rely on flash processing capabilities that could be leveraged to deliver malicious payloads.
Mitigation strategies for this vulnerability should prioritize immediate software updates to versions that have addressed the buffer overflow issue, as the maintainers have likely released patches containing proper bounds checking and memory allocation safeguards. System administrators should implement network segmentation and access controls to limit exposure of systems running swftools, while also considering the deployment of intrusion detection systems that can monitor for exploitation attempts. The vulnerability aligns with ATT&CK technique T1059.007 Command and Scripting Interpreter: JavaScript, as exploitation could involve JavaScript-based attack vectors targeting the flash processing capabilities. Additional defensive measures include implementing sandboxing techniques for flash file processing, deploying application whitelisting policies, and conducting regular security assessments to identify potential exploitation attempts. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates across all affected systems.