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HIGH

CVE-2018-20843

CVSS v3

7.5

HIGH

EPSS Score

7.1 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • mingw32-expatAlmaLinux:8all versions · fixed in 2.2.4-5.el8and 1 other package

Vendor advisories

  • CVE-2018-20843 Red Hat Product Security201 products fixed · 17 known affected

    expat: large number of colons in input makes parser consume high amount of resources, leading to DoS

    expat.src as a component of Red Hat Enterprise Linux 5 · xmlrpc-c.src as a component of Red Hat Enterprise Linux 5 · compat-expat1 as a component of Red Hat Enterprise Linux 6

  • RHSA-2025:22871 Red Hat Product Security2 products fixed

    Red Hat Security Advisory: expat security update

  • ICSA-23-348-10 CISA5 known affected

    Siemens SIMATIC S7-1500

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)

  • SSA-398330 Siemens ProductCERT5 known affected

    SSA-398330: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP >= V3.1.0 and < V3.1.5

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= V3.1.0 < V3.1.5 · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= V3.1.0 < V3.1.5 · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= V3.1.0 < V3.1.5

  • RHSA-2021:0949 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat OpenShift Do openshift/odo-init-image 1.1.3 security update

  • RHSA-2020:4484 Red Hat Product Security21 products fixed

    Red Hat Security Advisory: expat security update

4 more advisories

Full record on 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).

Technical details

Published
2019-06-24

Frequently asked questions

What is CVE-2018-20843?

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).

Is CVE-2018-20843 actively exploited?

Active exploitation of CVE-2018-20843 has not been confirmed. Its EPSS score was 7.1% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

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

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

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