CVE-2018-18718 in gThumb
Summary
by MITRE
An issue was discovered in gThumb through 3.6.2. There is a double-free vulnerability in the add_themes_from_dir method in dlg-contact-sheet.c because of two successive calls of g_free, each of which frees the same buffer.
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Analysis
by VulDB Data Team • 06/03/2023
The vulnerability identified as CVE-2018-18718 represents a critical double-free error in the gThumb image management application version 3.6.2 and earlier. This flaw exists within the dlg-contact-sheet.c source file where the add_themes_from_dir method contains a programming error that results in the same memory buffer being freed twice. The vulnerability stems from improper memory management practices where the application calls g_free function two times on what is essentially the same memory location, creating a condition that can be exploited by malicious actors to execute arbitrary code or cause application instability.
This double-free vulnerability falls under the Common Weakness Enumeration category CWE-415, which specifically addresses duplicate free conditions in software applications. The flaw demonstrates a classic memory corruption issue that can lead to undefined behavior when the application attempts to free the same memory block multiple times. When g_free is called twice on the same buffer, the first call properly deallocates the memory, but the second call attempts to free already released memory, potentially causing heap corruption that can be leveraged for privilege escalation or denial of service attacks.
The operational impact of this vulnerability extends beyond simple application crashes, as it can be exploited to execute arbitrary code within the context of the running gThumb process. Attackers could potentially craft malicious theme directories that, when processed by the vulnerable add_themes_from_dir method, trigger the double-free condition. This could result in remote code execution if the application processes untrusted theme files from network sources or local malicious actors gaining local privilege escalation capabilities. The vulnerability is particularly concerning in environments where gThumb is used to process user-uploaded content or when the application runs with elevated privileges.
Mitigation strategies for CVE-2018-18718 should prioritize immediate patching of the gThumb application to version 3.6.3 or later, which contains the necessary code fixes to prevent the double-free condition. System administrators should also implement additional security controls such as restricting user access to theme directories, implementing proper input validation for theme files, and monitoring for unusual application behavior that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1059.007 for command and script interpreter usage, as exploitation could involve crafting malicious theme files that trigger the vulnerability during normal application operation. Organizations should also consider implementing memory safety checks and address sanitization tools to detect similar issues in other applications that may be susceptible to heap corruption vulnerabilities.