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NVD / CVE Program· CNA redhat

CVE-2020-25708: A divide by zero issue was found to occur in libvncserver-0.9.12.

Noroxi assessment

Priority: Monitor (action score 30/100)

  • 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: 1.6% (FIRST EPSS); higher than 76.2% of all records.
  • 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.
  • Fixed version: libvncserver (AlmaLinux:8) 0.9.11-17.el8; libvncserver-devel (AlmaLinux:8) 0.9.11-17.el8; libvncserver (Debian:10) 0.9.11+dfsg-1.3+deb10u5.

Low priority for now. Upgrade to libvncserver (AlmaLinux:8) 0.9.11-17.el8; libvncserver-devel (AlmaLinux:8) 0.9.11-17.el8; libvncserver (Debian:10) 0.9.11+dfsg-1.3+deb10u5 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

A divide by zero issue was found to occur in libvncserver-0.9.12. A malicious client could use this flaw to send a specially crafted message that, when processed by the VNC server, would lead to a floating point exception, resulting in a denial of service.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Nov 27, 2020
Updated
Jun 16, 2026
EPSS
1.6% · 76th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.6%

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

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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
redhatenterprise linux
debiandebian linux

Affected versions

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

  • debian debian linux10.0
  • libvncserver project libvncserver0.9.12
  • redhat enterprise linux6.0
  • redhat enterprise linux7.0
  • redhat enterprise linux8.0

Versions reported by the vendor

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

  • n/a libvncserver

    • libvncserver 0.9.12affected

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:8libvncserverbefore 0.9.11-17.el80.9.11-17.el8
AlmaLinux:8libvncserver-develbefore 0.9.11-17.el80.9.11-17.el8
Debian:10libvncserverbefore 0.9.11+dfsg-1.3+deb10u50.9.11+dfsg-1.3+deb10u5
Debian:12libvncserverbefore 0.9.13+dfsg-10.9.13+dfsg-1
Debian:9libvncserverbefore 0.9.11+dfsg-1.3~deb9u60.9.11+dfsg-1.3~deb9u6
openSUSE:Leap 15.1LibVNCServerbefore 0.9.10-lp151.7.12.10.9.10-lp151.7.12.1
openSUSE:Leap 15.2LibVNCServerbefore 0.9.10-lp152.9.8.10.9.10-lp152.9.8.1
Red Hat:enterprise_linux:8::appstreamlibvncserverbefore 0:0.9.11-17.el80:0.9.11-17.el8
Red Hat:enterprise_linux:8::appstreamlibvncserver-debuginfobefore 0:0.9.11-17.el80:0.9.11-17.el8
Red Hat:enterprise_linux:8::appstreamlibvncserver-debugsourcebefore 0:0.9.11-17.el80:0.9.11-17.el8
Red Hat:enterprise_linux:8::crblibvncserver-develbefore 0:0.9.11-17.el80:0.9.11-17.el8
Rocky Linux:8libvncserverbefore 0:0.9.11-17.el80:0.9.11-17.el8
SUSE:HPE Helion OpenStack 8LibVNCServerbefore 0.9.9-17.34.10.9.9-17.34.1
SUSE:Linux Enterprise Module for Package Hub 15 SP1LibVNCServerbefore 0.9.10-4.25.10.9.10-4.25.1
SUSE:Linux Enterprise Point of Sale 11 SP3LibVNCServerbefore 0.9.1-160.22.10.9.1-160.22.1

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-2020-14400Jun 17, 2020 · An issue was discovered in LibVNCServer before 0.9.13.
    31Monitor
  • ← EarlierCVE-2020-14401Jun 17, 2020 · An issue was discovered in LibVNCServer before 0.9.13.
    27Monitor
  • Later →CVE-2020-29260Sep 2, 2022 · libvncclient v0.9.13 was discovered to contain a memory leak via the function rfbClientCleanup().
    30Monitor

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
almalinux:libvncserver0.9.11-17.el8 · AlmaLinux:8Package registry (OSV)
almalinux:libvncserver-devel0.9.11-17.el8 · AlmaLinux:8Package registry (OSV)
debian:libvncserver0.9.13+dfsg-1 · Debian:12Package registry (OSV)
opensuse:LibVNCServer0.9.10-lp152.9.8.1 · openSUSE:Leap 15.2Package registry (OSV)
red hat:libvncserver0:0.9.11-17.el8 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libvncserver-debuginfo0:0.9.11-17.el8 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libvncserver-debugsource0:0.9.11-17.el8 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
red hat:libvncserver-devel0:0.9.11-17.el8 · Red Hat:enterprise_linux:8::crbPackage registry (OSV)
rocky linux:libvncserver0:0.9.11-17.el8 · Rocky Linux:8Package registry (OSV)
suse:LibVNCServer0.9.1-160.22.1 · SUSE:Linux Enterprise Point of Sale 11 SP3Package 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.

No commit or PR link among the references.

Credits

All researchers

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

No credits in the CNA record.

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
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-369 · Divide By Zero

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

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

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

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

References

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

All records