CVE-2026-32853

A flaw was found in LibVNCServer. A malicious VNC server can exploit an improper bounds checking vulnerability in the UltraZip encoding handler, specifically within the HandleUltraZipBPP() function. By manipulating subrectangle header counts, an attacker can read beyond the allocated memory buffer. This heap out-of-bounds read can lead to information disclosure or cause the application to crash, resulting in a Denial of Service (DoS).

The availability impact of this flaw is limited on Red Hat products. While an attacker may be able to induce a crash in the LibVNCServer the host Red Hat system's availability is not at risk. Additionally, unless configured otherwise Red Hat Linux will automatically reboot LibVNCServer in the event of a crash.

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.