CVE-2017-11423 in libmspack
Summary
by MITRE
The cabd_read_string function in mspack/cabd.c in libmspack 0.5alpha, as used in ClamAV 0.99.2 and other products, allows remote attackers to cause a denial of service (stack-based buffer over-read and application crash) via a crafted CAB file.
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Analysis
by VulDB Data Team • 12/13/2022
The vulnerability identified as CVE-2017-11423 represents a critical stack-based buffer over-read flaw within the cabd_read_string function of libmspack version 0.5alpha. This issue specifically affects the CAB file decompression functionality and has been exploited in products including ClamAV 0.99.2, demonstrating the widespread impact of this particular vulnerability across multiple security applications. The flaw resides in the mspack/cabd.c source file where the function fails to properly validate input data lengths before processing CAB archive contents. This type of vulnerability falls under the CWE-121 category of stack-based buffer overflow, which is classified as a serious security weakness that can lead to arbitrary code execution or system instability. The vulnerability operates through a classic buffer over-read condition where the application attempts to read beyond the allocated memory boundaries when processing malformed CAB file structures.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can be leveraged by remote attackers to cause application crashes and potentially more severe system instability. When a maliciously crafted CAB file is processed by an affected system, the cabd_read_string function attempts to read memory locations that are beyond the intended buffer boundaries, resulting in unpredictable behavior including application termination, memory corruption, or potential privilege escalation in some scenarios. The attack vector is particularly concerning because it requires no special privileges or user interaction, making it a passive threat that can be exploited through automated scanning systems or when users unknowingly open compromised files. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under the T1203 category of Exploitation for Client Execution, where adversaries leverage application vulnerabilities to execute malicious code or cause system instability.
The remediation approach for CVE-2017-11423 involves immediate patching of the libmspack library to version 0.5alpha or later where the buffer over-read condition has been corrected through proper input validation and bounds checking mechanisms. Security administrators should prioritize updating all affected systems including ClamAV installations and any other products that utilize the vulnerable libmspack library. Additional mitigations include implementing strict file validation policies that scan CAB files before processing, deploying network-based intrusion detection systems that can identify and block suspicious file transfers, and establishing comprehensive monitoring protocols to detect application crashes or unusual behavior patterns. Organizations should also consider implementing sandboxing techniques for processing untrusted archive files and maintaining up-to-date threat intelligence feeds to identify new variants of malicious CAB files that may exploit similar vulnerabilities. The fix implemented in newer versions typically involves adding boundary checks before memory operations and ensuring that string parsing functions properly validate input lengths against allocated buffer sizes, preventing the stack-based buffer over-read condition that previously enabled remote code execution possibilities.