CVE-2018-20021

HIGHNVD 7.57.5—

7.5

LibVNC before commit c3115350eb8bb635d0fdb4dbbb0d0541f38ed19c contains a CWE-835: Infinite loop vulnerability in VNC client code. Vulnerability allows attacker to consume excessive amount of resources like CPU and RAM

CVSS v3: 7.5
EG Score: 7.5(medium)
EPSS: 85.7%
KEV: Not listed

Published

December 19, 2018

Last Modified

November 21, 2024

References (24)

vulnerability@kasperskyhttps://ics-cert.kaspersky.com/advisories/klcert-advisories/2018/12/19/klcert-18-031-libvnc-infinite-loop/
vulnerability@kasperskyhttps://lists.debian.org/debian-lts-announce/2018/12/msg00017.html
vulnerability@kasperskyhttps://lists.debian.org/debian-lts-announce/2019/10/msg00042.html
vulnerability@kasperskyhttps://lists.debian.org/debian-lts-announce/2019/11/msg00033.html
vulnerability@kasperskyhttps://lists.debian.org/debian-lts-announce/2019/12/msg00028.html
vulnerability@kasperskyhttps://security.gentoo.org/glsa/201908-05
vulnerability@kasperskyhttps://security.gentoo.org/glsa/202006-06
vulnerability@kasperskyhttps://usn.ubuntu.com/3877-1/
vulnerability@kasperskyhttps://usn.ubuntu.com/4547-1/
vulnerability@kasperskyhttps://usn.ubuntu.com/4547-2/
vulnerability@kasperskyhttps://usn.ubuntu.com/4587-1/
vulnerability@kasperskyhttps://www.debian.org/security/2019/dsa-4383
af854a3a-2127-422b-91ae-364da2661108https://ics-cert.kaspersky.com/advisories/klcert-advisories/2018/12/19/klcert-18-031-libvnc-infinite-loop/
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2018/12/msg00017.html
af854a3a-2127-422b-91ae-364da2661108https://lists.debian.org/debian-lts-announce/2019/10/msg00042.html

Patch Availability(4)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
ubuntu	libvncserver1 (0.9.11+dfsg-1.1ubuntu0.1) @ cosmic	2026-05-28	ubuntu
ubuntu	libitalccore (1:3.0.3+dfsg1-3ubuntu0.1) @ bionic	2026-05-28	ubuntu
ubuntu	ssvnc (1.0.29-2+deb8u1build0.16.04.1) @ xenial	2026-05-28	ubuntu
ubuntu	libitalccore (1:2.0.2+dfsg1-4ubuntu0.1) @ xenial	2026-05-28	ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-835Loop with Unreachable Exit Condition (Infinite Loop)

All Vendor Advisories

(4)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 9× in last 7d / 9× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-05-28 00:11 UTCEG score recompute
2026-05-28 00:11 UTCVendor advisory
2026-05-28 00:11 UTCGHSA enrichment
2026-05-27 13:38 UTCepss_batch
2026-05-27 13:38 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch

Frequently asked(5)

What is CVE-2018-20021?

CVE-2018-20021 is a high vulnerability published on December 19, 2018. LibVNC before commit c3115350eb8bb635d0fdb4dbbb0d0541f38ed19c contains a CWE-835: Infinite loop vulnerability in VNC client code. Vulnerability allows attacker to consume excessive amount of resources like CPU and RAM

When was CVE-2018-20021 disclosed?

CVE-2018-20021 was first published in the National Vulnerability Database on December 19, 2018, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2018-20021 actively exploited?

CVE-2018-20021 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 85.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2018-20021?

CVE-2018-20021 has a CVSS v3 base score of 7.5 (NVD).

How do I remediate CVE-2018-20021?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2018-20021, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2018-20021

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CVE-2018-20021

Published

Last Modified

References (24)

Patch Availability(4)

Weakness Classification(1)

All Vendor Advisories

Data Freshness Timeline

Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2018-20021?

Same vendor

Same CWE

CVE-2018-20021

📅 Published

🔄 Last Modified

🔗 References (24)

Patch Availability(4)

Weakness Classification(1)

All Vendor Advisories

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2018-20021?

🔗 Related CVEs(same vendor + same CWE)

Same vendor

Same CWE

Published

Last Modified

References (24)

Frequently asked(5)

Related CVEs(same vendor + same CWE)