CVE-2026-109089

A flaw was found in libXi. A heap-based buffer overflow vulnerability occurs when the library processes DEVICE_RESOLUTION data received from an X Window System server. A malicious or compromised X server can send crafted responses to a connecting client application, potentially leading to arbitrary code execution or causing a Denial of Service (DoS) through an application crash.

This vulnerability is rated as Important because malicious responses from an X server could cause memory corruption, potentially allowing arbitrary code execution within the privileges of the client application. On Red Hat Enterprise Linux systems, graphical applications typically communicate only with trusted, local display servers managed by the OS. Exploiting this condition requires a user or client program to explicitly connect to an untrusted or compromised external display server, which limits exposure in standard operational configurations.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.

--- CME Mitigation Guidance (2026-11-03) --- Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.

The highest-value action is to restrict graphical client applications from connecting to untrusted external X display servers to prevent malformed device control replies from reaching libXi: upgrade to libXi 1.8.4+ (or the fixed Libxi builds), which validate that the reply control matches the requested control and immediately jump to an exit path if they differ, closing all 2 injection vectors (mismatched DEVICE_RESOLUTION reply control values, crafted X server responses). Until patched, this is a concern on Linux client applications linked against libXi that issue XGetDeviceControl requests, so Prevent client applications from establishing connections to untrusted or external display servers, ensuring X11 traffic is restricted strictly to trusted local display servers managed by the OS. As a compensating measure, Enable Address Space Layout Randomization to randomize userspace memory addresses and impede shellcode execution or ROP gadget chaining, Enable Full RELRO and PIE to make the Global Offset Table read-only and randomize binary code pages against GOT overwrite techniques, Enable Control Flow Integrity or Shadow Call Stack to validate indirect branch targets and return addresses against control flow hijacking, and Enforce SELinux to confine the compromised client process to its domain and restrict access to system resources. These controls limit blast radius and contain exploitation, but they do not fix the underlying heap buffer overflow defect — apply the upstream patch to fully remediate.

Highest-impact CME: CME-301 SELinux (Enforcing Mode) (medium)