CVE-2021-39582 in SWFTools
Summary
by MITRE • 09/20/2021
An issue was discovered in swftools through 20200710. A heap-buffer-overflow exists in the function swf_GetPlaceObject() located in swfobject.c. It allows an attacker to cause code Execution.
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Analysis
by VulDB Data Team • 09/29/2021
The vulnerability CVE-2021-39582 represents a critical heap buffer overflow condition within the swftools software suite, specifically affecting versions through 20200710. This flaw resides within the swf_GetPlaceObject() function located in the swfobject.c source file, making it a direct consequence of improper memory management practices during the parsing of swf file formats. The issue stems from the software's failure to properly validate buffer boundaries when processing certain swf file structures, particularly those involving place object operations that define how elements are positioned within flash animations.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious swf file that triggers the heap buffer overflow during the execution of swf_GetPlaceObject(). This function processes place object records within swf files, which contain positioning and transformation data for graphical elements. When the software attempts to read or write data beyond allocated memory boundaries, it creates opportunities for arbitrary code execution. The heap corruption can be leveraged by attackers to overwrite critical memory locations, potentially leading to privilege escalation or complete system compromise. This vulnerability aligns with CWE-121, heap-based buffer overflow, which specifically addresses buffer overflows occurring in heap memory regions where memory is dynamically allocated and deallocated.
The operational impact of CVE-2021-39582 extends beyond simple denial of service scenarios, as it enables remote code execution capabilities that can be exploited across various attack vectors. Systems utilizing swftools for swf file processing, conversion, or analysis become vulnerable when handling untrusted swf content, including web applications that embed flash content or file processing systems that handle swf files as part of their workflow. The vulnerability is particularly concerning in environments where swf files are processed automatically or when users can upload or download swf content without proper validation. Attackers can leverage this flaw to execute malicious code with the privileges of the affected process, potentially leading to full system compromise, data exfiltration, or establishment of persistent backdoors within the target environment.
Mitigation strategies for CVE-2021-39582 should prioritize immediate software updates to versions that have addressed the heap buffer overflow issue through proper memory boundary validation. Organizations should implement strict input validation for all swf file processing, including sanitization of file headers and content structures before parsing. The principle of least privilege should be enforced when running swftools, limiting the execution environment to minimal required permissions and isolating processing in sandboxed environments. Network segmentation and monitoring should be implemented to detect potential exploitation attempts, particularly when swf files are processed from untrusted sources. Additionally, regular security assessments of swf processing workflows should be conducted to identify similar vulnerabilities in other components of the software stack, aligning with ATT&CK technique T1059.007 for command and scripting interpreter and T1203 for Exploitation for Client Execution, which encompass the typical attack patterns associated with such buffer overflow vulnerabilities in multimedia processing tools.