CVE-2021-44590 in libming
Summary
by MITRE • 01/06/2022
In libming 0.4.8, a memory exhaustion vulnerability exist in the function cws2fws in util/main.c. Remote attackers could launch denial of service attacks by submitting a crafted SWF file that exploits this vulnerability.
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Analysis
by VulDB Data Team • 01/09/2022
The vulnerability identified as CVE-2021-44590 represents a critical memory exhaustion flaw within libming version 0.4.8, specifically affecting the cws2fws function located in util/main.c. This issue manifests as a denial of service condition that can be exploited remotely through the submission of maliciously crafted SWF files, making it particularly dangerous in web-based environments where SWF content is processed. The vulnerability stems from inadequate memory management within the function responsible for converting compressed SWF (cws) to full SWF (fws) format, creating a scenario where memory allocation becomes excessive and uncontrolled during the processing of malformed input files.
The technical nature of this flaw aligns with CWE-401, which categorizes memory leaks and memory exhaustion issues in software systems. The cws2fws function appears to lack proper bounds checking and memory allocation limits when handling compressed SWF data structures, allowing attackers to craft SWF files that trigger excessive memory consumption patterns. This vulnerability operates at the intersection of software parsing and resource management, where the legitimate processing of compressed binary data becomes a vector for resource exhaustion attacks. The flaw essentially allows an attacker to cause the application to allocate increasingly large amounts of memory without proper constraints, leading to system instability and potential application crashes.
From an operational standpoint, this vulnerability presents significant risks to systems that process SWF files, particularly web servers, content management systems, and media processing applications that accept user-uploaded Flash content. The remote exploitation capability means that attackers can trigger the denial of service condition without requiring local access or authentication, making it particularly dangerous in public-facing applications. The impact extends beyond simple service disruption to potentially affecting system availability for legitimate users, as the memory exhaustion can cause the entire application or system to become unresponsive or crash entirely. This vulnerability directly maps to ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a classic example of resource exhaustion attacks that can be executed through malformed input processing.
Mitigation strategies for CVE-2021-44590 should focus on immediate patching of the libming library to version 0.4.9 or later, which contains the necessary fixes for the memory management issues in the cws2fws function. Organizations should implement input validation and size limiting mechanisms for all SWF file processing to prevent malicious files from reaching the vulnerable code path. Additionally, deploying application firewalls or web application firewalls that can detect and block suspicious SWF file patterns can provide an additional layer of protection. System administrators should also consider implementing memory monitoring and alerting mechanisms to detect unusual memory consumption patterns that might indicate exploitation attempts. The vulnerability underscores the importance of proper resource management in binary format parsers and highlights the need for comprehensive testing of input handling routines to prevent similar issues in other software components.