Is CVE-2018-20843 in the CISA KEV catalog?

No. CVE-2018-20843 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2018-20843?

CVE-2018-20843 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2018-20843?

CVE-2018-20843 has an EPSS score of 7.11% (93th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2018-20843?

Upgrade expat on debian 11 to 2.2.6-2 or later. Fixes are available for 18 affected products.

CVE & CISA-KEV Catalog

CVE-2018-20843

HIGHEPSS 93th pctl

7.5

CVSS v3

NVD

Description

In libexpat in Expat before 2.2.7, XML input including XML names that contain a large number of colons could make the XML parser consume a high amount of RAM and CPU resources while processing (enough to be usable for denial-of-service attacks).

CWE-611XML External Entity (XXE)

How to fix

Remediation Available

expatDebian

Fixed in:2.2.6-2CVE-2018-20843

expatRed Hat / RHEL

Fixed in:0:2.2.10-1.el8_2RHSA-2025:22871

expatRocky

Fixed in:0:2.2.10-1.el8_2RHSA-2025:22871

expat-debuginfoRed Hat / RHEL

Fixed in:0:2.2.10-1.el8_2RHSA-2025:22871

expat-debuginfoRocky

Fixed in:0:2.2.10-1.el8_2RHSA-2025:22871

expat-debugsourceRocky

Fixed in:0:2.2.10-1.el8_2RHSA-2025:22871

expat-debugsourceRed Hat / RHEL

Fixed in:0:2.2.10-1.el8_2RHSA-2025:22871

expat-develRed Hat / RHEL

Fixed in:0:2.2.10-1.el8_2RHSA-2025:22871

expat-develRocky

Fixed in:0:2.2.10-1.el8_2RHSA-2025:22871

expatUbuntu

Fixed in:2.1.0-4ubuntu1.4+esm1USN-4040-2

Fixed in:2.1.0-7ubuntu0.16.04.4USN-4040-1

Fixed in:2.2.5-3ubuntu0.1USN-4040-1

lib64expat1Ubuntu

Fixed in:2.1.0-4ubuntu1.4+esm1USN-4040-2

Fixed in:2.1.0-7ubuntu0.16.04.4USN-4040-1

libexpat1Ubuntu

Fixed in:2.1.0-4ubuntu1.4+esm1USN-4040-2

Fixed in:2.1.0-7ubuntu0.16.04.4USN-4040-1

Fixed in:2.2.5-3ubuntu0.1USN-4040-1

libvtk5.10Ubuntu

Fixed in:5.10.1+dfsg-2.1ubuntu0.1~esm1USN-4852-1

libvtk5.8Ubuntu

Fixed in:5.8.0-14.1ubuntu3+esm1USN-4852-1

libxmltokUbuntu

Fixed in:1.2-3ubuntu0.16.04.1~esm2USN-5455-1

Fixed in:1.2-4ubuntu0.18.04.1~esm4USN-7199-1

Fixed in:1.2-4ubuntu0.18.04.1~esm1USN-5455-1

Fixed in:1.2-4ubuntu0.20.04.1~esm4USN-7199-1

Fixed in:1.2-4ubuntu0.20.04.1~esm1USN-5455-1

Fixed in:1.2-4ubuntu0.22.04.1~esm4USN-7199-1

Fixed in:1.2-4ubuntu0.22.04.1~esm1USN-5455-1

Fixed in:1.2-4.1ubuntu2.24.0.4.1+esm2USN-7199-1

libxmltok1Ubuntu

Fixed in:1.2-3ubuntu0.16.04.1~esm2USN-5455-1

Fixed in:1.2-4ubuntu0.18.04.1~esm4USN-7199-1

Fixed in:1.2-4ubuntu0.18.04.1~esm1USN-5455-1

Fixed in:1.2-4ubuntu0.20.04.1~esm4USN-7199-1

Fixed in:1.2-4ubuntu0.20.04.1~esm1USN-5455-1

Fixed in:1.2-4ubuntu0.22.04.1~esm4USN-7199-1

Fixed in:1.2-4ubuntu0.22.04.1~esm1USN-5455-1

libxmltok1t64Ubuntu

Fixed in:1.2-4.1ubuntu2.24.0.4.1+esm2USN-7199-1

vtkUbuntu

Fixed in:5.8.0-14.1ubuntu3+esm1USN-4852-1

Fixed in:5.10.1+dfsg-2.1ubuntu0.1~esm1USN-4852-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

7.11%probability of exploitation in 30 days

93rdpercentile

High risk: more likely to be exploited than 93% of all known CVEs.

References

Related Vulnerabilities

Other CWE-611 (XML External Entity (XXE)) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-34102	Critical	9.8	100%	KEV	Fix
CVE-2019-9670	Critical	9.8	100%	KEV	Fix
CVE-2022-28219	Critical	9.8	97%	-	-
CVE-2024-22024	High	8.3	95%	-	-
CVE-2024-38653	High	7.5	92%	-	-
CVE-2017-12629	Critical	9.8	92%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-05-30.