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NVD / CVE Program· CNA VulnCheck

CVE-2026-32853: LibVNCServer UltraZip Encoding Heap Out-of-bounds Read

Noroxi assessment

Priority: Monitor (action score 27/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.44% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: 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.

Low priority for now. Upgrade to 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 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 6.9 · v4.0—No exploit Fix available
Published
Mar 24, 2026
Updated
Jul 14, 2026
EPSS
0.4% · 38th percentile

Report tools

JSON

Action score

27

Monitor

Low priority for now.

CVSS
27 / 40 · 6.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
proof of concept
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · VulnCheck
6.9
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-32853

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
libvncserver projectlibvncserver

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • libvncserver project libvncserverbefore 0.9.15

Versions reported by the vendor

Affected version ranges reported by the assigning authority (VulnCheck). Independent of NVD's CPE analysis and usually ahead of it.

  • LibVNC LibVNCServer

    • 009008e2f4d5a54dd71f422070df3af7b3dbc931not affected
    • up to and including 0.9.15affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12libvncserverbefore 0.9.14+dfsg-1+deb12u10.9.14+dfsg-1+deb12u1
Debian:13libvncserverbefore 0.9.15+dfsg-1+deb13u10.9.15+dfsg-1+deb13u1
Debian:14libvncserverbefore 0.9.15+dfsg-30.9.15+dfsg-3
openSUSE:Leap 15.6LibVNCServerbefore 0.9.14-150600.3.6.10.9.14-150600.3.6.1
openSUSE:Leap 16.0LibVNCServerbefore 0.9.14-160000.4.10.9.14-160000.4.1
openSUSE:TumbleweedLibVNCServerbefore 0.9.15-2.10.9.15-2.1
SUSE:Linux Enterprise Module for Package Hub 15 SP7LibVNCServerbefore 0.9.14-150600.3.6.10.9.14-150600.3.6.1
SUSE:Linux Enterprise Module for Package Hub 15 SP7LibVNCServerbefore 0.9.10-150000.4.35.10.9.10-150000.4.35.1
SUSE:Linux Enterprise Server 12 SP5-LTSSLibVNCServerbefore 0.9.9-17.44.10.9.9-17.44.1
SUSE:Linux Enterprise Server 16.0LibVNCServerbefore 0.9.14-160000.4.10.9.14-160000.4.1

Same product

libvncserver project: all records

Other highest-scoring records for the same primary product.

  • CVE-2018-7225An issue was discovered in LibVNCServer through 0.9.11.
    41Plan
  • CVE-2017-18922It was discovered that websockets.c in LibVNCServer prior to 0.9.12 did not properly decode certain WebSocket frames.
    40Plan
  • CVE-2016-9942Heap-based buffer overflow in ultra.c in LibVNCClient in LibVNCServer before 0.9.11 allows remote servers to cause a denial of service (appl
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2020-25708Nov 27, 2020 · A divide by zero issue was found to occur in libvncserver-0.9.12.
    30Monitor
  • ← EarlierCVE-2020-29260Sep 2, 2022 · libvncclient v0.9.13 was discovered to contain a memory leak via the function rfbClientCleanup().
    30Monitor
  • Later →CVE-2026-32854Mar 24, 2026 · LibVNCServer httpd proxy NULL Pointer Dereference
    27Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:libvncserver0.9.14+dfsg-1+deb12u1 · Debian:12Package registry (OSV)
opensuse:LibVNCServer0.9.14-150600.3.6.1 · openSUSE:Leap 15.6Package registry (OSV)
suse:LibVNCServer0.9.10-150000.4.35.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP7Package registry (OSV)
suse:LibVNCServer0.9.14-150600.3.6.1 · SUSE:Linux Enterprise Module for Package Hub 15 SP7Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-125 · Out-of-bounds Read

CVSS vector

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-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records