Bug 2450843 (CVE-2026-32853)

Summary: CVE-2026-32853 LibVNCServer: LibVNCServer: Information disclosure or Denial of Service via heap out-of-bounds read in UltraZip encoding
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: crizzo
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
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).
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2450886, 2450887    
Bug Blocks:    

Description OSIDB Bzimport 2026-03-24 18:01:49 UTC 
LibVNCServer versions 0.9.15 and prior (fixed in commit 009008e) contain a heap out-of-bounds read vulnerability in the UltraZip encoding handler that allows a malicious VNC server to cause information disclosure or application crash. Attackers can exploit improper bounds checking in the HandleUltraZipBPP() function by manipulating subrectangle header counts to read beyond the allocated heap buffer.