CVE-2018-11226 in libming
Summary
by MITRE
The getString function in decompile.c in libming through 0.4.8 mishandles cases where the header indicates a file size greater than the actual size, which allows remote attackers to cause a denial of service (Segmentation fault and application crash) or possibly have unspecified other impact.
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Analysis
by VulDB Data Team • 03/14/2023
The vulnerability identified as CVE-2018-11226 resides within the libming library version 0.4.8 and earlier, specifically affecting the getString function implementation in decompile.c. This flaw represents a classic buffer over-read condition that occurs when processing SWF file headers, where the library fails to properly validate the relationship between the declared file size in the header and the actual data available in the file. The issue manifests when the header indicates a file size that exceeds the actual data size, creating a scenario where the decompilation process attempts to read beyond the allocated buffer boundaries, leading to unpredictable behavior and system instability.
The technical exploitation of this vulnerability stems from improper input validation mechanisms within the getString function, which operates without adequate bounds checking when processing malformed SWF files. When an attacker crafts a specially formatted SWF file with a header indicating an oversized file size, the decompile.c module attempts to access memory locations beyond the legitimate data boundaries, resulting in segmentation faults and application crashes. This behavior aligns with CWE-129, which describes improper validation of length fields, and specifically manifests as a form of buffer over-read vulnerability that can be leveraged for denial of service attacks. The vulnerability's impact extends beyond simple crashes, as the unpredictable memory access patterns may potentially enable more sophisticated exploitation techniques depending on the execution environment and memory layout.
From an operational perspective, this vulnerability presents significant risks to systems that process untrusted SWF content, particularly web applications, content management systems, and media processing platforms that utilize libming for SWF file handling. The remote attack vector means that adversaries can trigger the vulnerability through web-based file uploads, embedded SWF content, or any mechanism that processes external SWF files without proper sanitization. The potential for unspecified other impacts suggests that under certain conditions, this vulnerability might be exploitable for additional security consequences beyond simple denial of service, potentially including information disclosure or privilege escalation depending on the target environment and the specific implementation details of the affected applications. The ATT&CK framework categorizes this as a denial of service attack through resource exhaustion and memory corruption techniques, which can be classified under the T1499.004 sub-technique related to network denial of service.
Mitigation strategies for CVE-2018-11226 should focus on immediate patching of affected libming versions to 0.4.9 or later, where the vulnerability has been addressed through proper bounds checking and input validation. Organizations should implement comprehensive file validation mechanisms that verify header integrity before processing SWF content, particularly in web-facing applications where untrusted user uploads are possible. Network-based mitigations could include implementing strict file format validation at ingress points and deploying sandboxed environments for SWF file processing. Additionally, application-level protections should enforce memory safety checks and implement proper error handling for malformed input, ensuring that any buffer over-read conditions are gracefully managed without system crashes. The vulnerability serves as a reminder of the critical importance of input validation and bounds checking in multimedia processing libraries, where malformed file formats can lead to severe security implications.