Out-of-bounds read in LibVNCServer - CVE-2026-32853

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Main Vulnerability Database Vulnerabilities #VU128150

Out-of-bounds read in LibVNCServer - CVE-2026-32853

Published: April 27, 2026


Vulnerability identifier: #VU128150
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-32853
CWE-ID: CWE-125
Exploitation vector: Remote access
Exploit availability: No public exploit available

Vulnerability details

The vulnerability allows a remote attacker to disclose sensitive information or cause a denial of service.

The vulnerability exists due to out-of-bounds read in the HandleUltraZipBPP function in src/libvncclient/ultra.c when processing UltraZip-encoded FramebufferUpdate messages. A remote attacker can send a specially crafted FramebufferUpdate message with an attacker-controlled subrectangle count to disclose sensitive information or cause a denial of service.

UltraZip encoding is enabled by default in LibVNCClient, and no authentication is required on the server side when using rfbSecTypeNone.


Affected software

LibVNCServer
SUSE Linux Enterprise Server 12 SP5 LTSS Extended
SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise High Performance Computing 12
SUSE Linux Enterprise Server 12
SUSE Linux Enterprise Real Time 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Desktop 15
SUSE Linux Enterprise Workstation Extension 15
SUSE Package Hub 15
openSUSE Leap
openEuler
Anolis OS
libvncclient0-debuginfo
libvncclient0
libvncserver0-debuginfo
LibVNCServer-debugsource
libvncserver0
LibVNCServer-devel
libvncserver-devel
libvncserver-debugsource
libvncserver
libvncserver-debuginfo
libvncserver1
libvncclient1
libvncserver1-debuginfo
libvncclient1-debuginfo
libvncserver-doc

How to mitigate CVE-2026-32853

Install security update from vendor's website.

libvncclient0-debuginfo - update to 0.9.9-17.44.1
libvncclient0 - update to 0.9.9-17.44.1
libvncserver0-debuginfo - addressed in versions 0.9.9-17.44.1, 0.9.10-150000.4.35.1
LibVNCServer-debugsource - addressed in versions 0.9.9-17.44.1, 0.9.10-150000.4.35.1, 0.9.14-150600.3.6.1
libvncserver0 - addressed in versions 0.9.9-17.44.1, 0.9.10-150000.4.35.1
LibVNCServer-devel - addressed in versions 0.9.9-17.44.1, 0.9.14-150600.3.6.1
libvncserver-devel - update to 0.9.13-4
libvncserver-debugsource - update to 0.9.13-4
libvncserver - update to 0.9.13-4
libvncserver-debuginfo - update to 0.9.13-4
libvncserver1 - update to 0.9.14-150600.3.6.1
libvncclient1 - update to 0.9.14-150600.3.6.1
libvncserver1-debuginfo - update to 0.9.14-150600.3.6.1
libvncclient1-debuginfo - update to 0.9.14-150600.3.6.1
libvncserver-doc - update to 0.9.15-1
libvncserver-devel - update to 0.9.15-1
libvncserver - update to 0.9.15-1

External References

Related Security Bulletins