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CVE-2020-14398: An issue was discovered in LibVNCServer before 0.9.13

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HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2020-14398 is a high-severity flaw (CVSS 7.5) affecting libvncserver, ubuntu linux, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in LibVNCServer before 0.9.13. An improperly closed TCP connection causes an infinite loop in libvncclient/sockets.c.

Why this priority

  • High severity
  • Remotely exploitable, no login, no user action
  • On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score7.5 (High)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance2.7% (top 14%)
CISA exploited listNo
WeaknessCWE-835
Published2020-06-17
Last modified2026-06-17
Publisher (CNA): MITRE · Vendor: canonical · debian · libvnc project · siemens

Share: LinkedIn · X · Reddit

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

libvnc project libvncserver UPGRADE
Affected: <= 0.9.12
Fixed in: newer than 0.9.12
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy libvncserver || rpm -q libvncserver || libvncserver --version
2. UPGRADE to newer than 0.9.12 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade libvncserver
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade libvncserver
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
canonical ubuntu linux MITIGATE
Affected: 14.04 · 16.04 · 18.04 · 18.10 · 20.04
Fixed in: no fixed release known
Safe to downgrade to: a release before 14.04
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
debian debian linux MITIGATE
Affected: 8.0 · 9.0
Fixed in: no fixed release known
Safe to downgrade to: a release before 8.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
siemens simatic itc1500 firmware UPGRADE
Affected: >= 3.0.0.0 and < 3.2.1.0
Fixed in: 3.2.1.0
Safe to downgrade to: a release before 3.0.0.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
siemens simatic itc1500 pro firmware UPGRADE
Affected: >= 3.0.0.0 and < 3.2.1.0
Fixed in: 3.2.1.0
Safe to downgrade to: a release before 3.0.0.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
siemens simatic itc1900 firmware UPGRADE
Affected: >= 3.0.0.0 and < 3.2.1.0
Fixed in: 3.2.1.0
Safe to downgrade to: a release before 3.0.0.0
Check your OS release
cat /etc/os-release; uname -r
Debian / Ubuntu
sudo apt update && sudo apt full-upgrade
RHEL / Amazon Linux / Fedora
sudo dnf upgrade --refresh
Windows
Install the latest cumulative update from Windows Update
If no patch exists yet
OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-14398?

libvncserver: upgrade to newer than 0.9.12; ubuntu linux: mitigate or apply the listed mitigation; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-14398 being exploited?

CVE-2020-14398 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-14398 affect?

CVE-2020-14398 affects libvncserver, ubuntu linux, debian linux. Severity is high (CVSS 7.5). An issue was discovered in LibVNCServer before 0.9.13. An improperly closed TCP connection causes an infinite loop in libvncclient/sockets.c.

How urgent is CVE-2020-14398?

Priority 58/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Ubuntu vulnerabilities · Debian vulnerabilities · Siemens vulnerabilities

Related CVEs

References

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