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Fencer Vulns
high 8.1

CVE-2026-32853 json

LibVNCServer UltraZip Encoding Heap Out-of-bounds Read

published 2026-03-24 7 mo ago modified 2026-11-08 23 h ago also EUVD-2026-14930

cvss
8.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

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.

Patch / fix

  • libvncserver_project libvncserver 0.9.15
  • libvncserver Debian 12 0.9.14+dfsg-1+deb12u1
  • libvncserver Debian 13 0.9.15+dfsg-1+deb13u1
  • libvncserver Debian 14 0.9.15+dfsg-3

debian advisories DEBIAN-CVE-2026-32853

  • libvncserver Ubuntu 22.04 LTS 0.9.13+dfsg-3ubuntu0.1
  • libvncserver Ubuntu 24.04 LTS 0.9.14+dfsg-1ubuntu0.1
  • libvncserver Ubuntu 25.10 0.9.15+dfsg-1ubuntu0.1

ubuntu advisories UBUNTU-CVE-2026-32853

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • LibVNCServer SLES for SAP applications 16.0, SLES 16.0 0.9.14-160000.4.1
  • LibVNCServer SLE Workstation Extension 15 SP7, SLE Module for Package Hub 15 SP7, openSUSE Leap 15.6 0.9.14-150600.3.6.1
  • LibVNCServer SLE Module for Package Hub 15 SP7 0.9.10-150000.4.35.1
  • LibVNCServer SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 0.9.9-17.44.1

suse advisories SUSE-SU-2026:21206-1SUSE-SU-2026:1174-1SUSE-SU-2026:1173-1SUSE-SU-2026:1124-1

  • LibVNCServer openSUSE Leap 16.0 0.9.14-160000.4.1
  • LibVNCServer openSUSE Tumbleweed 0.9.15-2.1

opensuse advisories openSUSE-SU-2026:20552-1openSUSE-SU-2026:10433-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-32853 updated cvss 5.4

LibVNCServer: LibVNCServer: Information disclosure or Denial of Service via heap out-of-bounds read in UltraZip encoding

  • Red Hat Enterprise Linux 6 libvncserver
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Enterprise Linux 8 libvncserver
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Enterprise Linux 9 gnome-remote-desktop
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 7 libvncserver
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.45% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/LibVNC/libvncserver/security/advisories/GHSA-87q7-v983-qwcj referenced PoC, tagged "exploit" by a source, unverified
  • vulncheck.com https://www.vulncheck.com/advisories/libvncserver-ultrazip-encoding-heap-out-of-bounds-read referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 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
CNA 4.0 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H

Affected products

  • LibVNC LibVNCServer

Classification

Weakness

References

Sources

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