CVE-2018-14600 in libX11
Summary
by MITRE
An issue was discovered in libX11 through 1.6.5. The function XListExtensions in ListExt.c interprets a variable as signed instead of unsigned, resulting in an out-of-bounds write (of up to 128 bytes), leading to DoS or remote code execution.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 05/04/2023
The vulnerability identified as CVE-2018-14600 resides within the libX11 library version 1.6.5 and earlier, representing a critical memory corruption flaw that affects the X Window System implementation. This issue manifests in the XListExtensions function located in the ListExt.c source file, where a fundamental type interpretation error creates a dangerous condition that can be exploited by malicious actors. The flaw stems from the improper handling of a variable that should be treated as unsigned but is instead interpreted as signed, creating a pathway for attackers to manipulate memory boundaries.
The technical implementation of this vulnerability involves a classic buffer overflow scenario where the signed interpretation of an unsigned variable leads to an out-of-bounds write operation. When the XListExtensions function processes extension information, it calculates buffer sizes based on incorrectly interpreted signed values, allowing attackers to write up to 128 bytes beyond the intended memory boundaries. This memory corruption directly violates the fundamental principles of secure coding practices and represents a clear violation of CWE-121, which addresses stack-based buffer overflow conditions. The vulnerability is particularly dangerous because it can be triggered through legitimate X11 protocol interactions, making it accessible to remote attackers who can craft malicious X11 requests to exploit this condition.
The operational impact of CVE-2018-14600 extends beyond simple denial of service to encompass potential remote code execution capabilities, making it a severe threat to systems relying on X11 for graphical interfaces. Systems running vulnerable versions of libX11, particularly those with network-accessible X11 servers, become prime targets for exploitation. The vulnerability affects desktop environments, remote desktop solutions, and any application that depends on X11 for graphical rendering, creating a broad attack surface that spans from individual workstations to enterprise server environments. Attackers can leverage this flaw to execute arbitrary code on targeted systems, potentially leading to complete system compromise and unauthorized access to sensitive data.
Mitigation strategies for CVE-2018-14600 require immediate patching of affected libX11 installations to version 1.6.6 or later, which contains the necessary fixes to correct the variable type interpretation. Organizations should also implement network segmentation to limit access to X11 servers and consider disabling unnecessary X11 forwarding capabilities in SSH configurations. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1059, which covers command and script injection, as exploitation could enable attackers to execute malicious code on compromised systems. Additionally, implementing proper input validation and boundary checking mechanisms can help prevent similar issues in other software components, while regular security audits of third-party libraries can identify other potential vulnerabilities before they can be exploited by adversaries.