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Vulnerability details: VCID-jc77-4mmq-yfgc
Vulnerability ID VCID-jc77-4mmq-yfgc
Aliases CVE-2018-20021
Summary 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
Status Published
Exploitability 0.5
Weighted Severity 7.0
Risk 3.5
Affected and Fixed Packages Package Details
Weaknesses (2)
CWE-835 Loop with Unreachable Exit Condition ('Infinite Loop')
CWE-400 Uncontrolled Resource Consumption
System Score Found at
cvssv3 6.5 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2018-20021.json
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
epss 0.02642 https://api.first.org/data/v1/epss?cve=CVE-2018-20021
cvssv3 6.5 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv2 7.8 https://nvd.nist.gov/vuln/detail/CVE-2018-20021
cvssv3 7.5 https://nvd.nist.gov/vuln/detail/CVE-2018-20021
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2018-20021.json
https://api.first.org/data/v1/epss?cve=CVE-2018-20021
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-15126
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-15127
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-20019
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-20020
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-20021
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-20022
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-20023
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-20024
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-21247
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-6307
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://ics-cert.kaspersky.com/advisories/klcert-advisories/2018/12/19/klcert-18-031-libvnc-infinite-loop/
https://lists.debian.org/debian-lts-announce/2018/12/msg00017.html
https://lists.debian.org/debian-lts-announce/2019/10/msg00042.html
https://lists.debian.org/debian-lts-announce/2019/11/msg00033.html
https://lists.debian.org/debian-lts-announce/2019/12/msg00028.html
https://security.gentoo.org/glsa/201908-05
https://security.gentoo.org/glsa/202006-06
https://www.debian.org/security/2019/dsa-4383
1661120 https://bugzilla.redhat.com/show_bug.cgi?id=1661120
916941 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=916941
cpe:2.3:a:libvnc_project:libvncserver:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:libvnc_project:libvncserver:*:*:*:*:*:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
CVE-2018-20021 https://nvd.nist.gov/vuln/detail/CVE-2018-20021
USN-3877-1 https://usn.ubuntu.com/3877-1/
USN-4547-1 https://usn.ubuntu.com/4547-1/
USN-4547-2 https://usn.ubuntu.com/4547-2/
USN-4587-1 https://usn.ubuntu.com/4587-1/
No exploits are available.
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2018-20021.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Found at https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: AV:N/AC:L/Au:N/C:N/I:N/A:C Found at https://nvd.nist.gov/vuln/detail/CVE-2018-20021
Exploitability (E) Access Vector (AV) Access Complexity (AC) Authentication (Au) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

high

functional

unproven

proof_of_concept

not_defined

local

adjacent_network

network

high

medium

low

multiple

single

none

none

partial

complete

none

partial

complete

none

partial

complete
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://nvd.nist.gov/vuln/detail/CVE-2018-20021
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.85152
EPSS Score 0.02642
Published At July 30, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:36:00.648917+00:00 Ubuntu USN Importer Import https://usn.ubuntu.com/4547-2/ 37.0.0