CVE-2017-12177 in X11 Server
Summary
by MITRE
xorg-x11-server before 1.19.5 was vulnerable to integer overflow in ProcDbeGetVisualInfo function allowing malicious X client to cause X server to crash or possibly execute arbitrary code.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 08/29/2025
The vulnerability identified as CVE-2017-12177 affects the xorg-x11-server component prior to version 1.19.5, specifically within the ProcDbeGetVisualInfo function. This represents a critical integer overflow condition that can be exploited by malicious X client applications to compromise the security and stability of the X Window System server. The issue stems from improper input validation and arithmetic handling within the server's Dbe (Double Buffering Extension) implementation, creating a scenario where carefully crafted malicious requests can trigger unexpected behavior in the server's memory management operations.
The technical flaw manifests as an integer overflow within the ProcDbeGetVisualInfo function, which processes requests related to visual information in the double buffering extension. When a malicious X client sends a specially constructed request with oversized parameters, the server's arithmetic operations fail to properly validate the input values, leading to integer overflow conditions that can corrupt memory structures. This vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, specifically affecting the X Window System's server-side processing of client requests. The overflow occurs during calculations involving visual attributes and buffer management, where the server attempts to allocate memory or process data structures based on malicious input values that exceed normal operational bounds.
The operational impact of this vulnerability extends beyond simple server crashes to potentially enable arbitrary code execution on the target system. When exploited successfully, the integer overflow can cause the X server to behave unpredictably, leading to denial of service conditions or more severe consequences where the attacker can manipulate memory contents to execute arbitrary code with the privileges of the X server process. This represents a significant risk to systems running X Window System environments, particularly in multi-user scenarios where malicious clients could exploit this vulnerability to gain unauthorized access to system resources or compromise the entire graphical environment. The vulnerability affects systems where the X server is running with elevated privileges, making it particularly dangerous in enterprise and server environments.
Mitigation strategies for CVE-2017-12177 primarily focus on upgrading to xorg-x11-server version 1.19.5 or later, which contains the necessary patches to address the integer overflow condition. System administrators should prioritize applying security updates and patches from their respective distribution vendors to ensure the X server is protected against this vulnerability. Additionally, implementing network segmentation and access controls to limit X client connections can reduce the attack surface, while monitoring for unusual X server behavior or excessive resource consumption can help detect potential exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1059.007 for command and scripting interpreter and T1499.004 for network denial of service, as exploitation can lead to both service disruption and potential code execution. Organizations should also consider implementing application whitelisting policies to restrict which X clients can connect to the server, reducing the likelihood of successful exploitation through malicious client applications.