CVE-2021-43818

Name: CVE-2021-43818
Creator: NVD / NIST
Published: 2021-12-13T18:15:08.387+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.1/10EPSS 2.46%

Last modified Jun 17, 2026

CVE-2021-43818 is a high-severity vulnerability rated 7.1/10 on the CVSS scale. lxml is a library for processing XML and HTML in the Python language. Prior to version 4.6.5, the HTML Cleaner in lxml.html lets certain crafted script content pass through, as well as script content in SVG files embedded using data URIs. EPSS estimates a 2.46% chance of exploitation in the next 30 days.

Description

lxml is a library for processing XML and HTML in the Python language. Prior to version 4.6.5, the HTML Cleaner in lxml.html lets certain crafted script content pass through, as well as script content in SVG files embedded using data URIs. Users that employ the HTML cleaner in a security relevant context should upgrade to lxml 4.6.5 to receive a patch. There are no known workarounds available.

Metrics

CVSS 3.1

7.1/10

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

EPSS Probability

2.46%

82.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Lxml	Lxml	< 4.6.5
Fedoraproject	Fedora	34
Fedoraproject	Fedora	35
Debian	Debian Linux	9.0
Debian	Debian Linux	10.0
Debian	Debian Linux	11.0
Netapp	Solidfire	All versions
Netapp	Solidfire Enterprise Sds	All versions
Netapp	Hci Storage Node Firmware	All versions
Oracle	Communications Cloud Native Core Binding Support Function	22.1.3
Oracle	Communications Cloud Native Core Network Exposure Function	22.1.1
Oracle	Communications Cloud Native Core Policy	22.2.0
Oracle	Http Server	12.2.1.3.0
Oracle	Http Server	12.2.1.4.0
Oracle	Zfs Storage Appliance Kit	8.8

References

https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664aPatch, Third Party Advisory
https://github.com/lxml/lxml/commit/a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c#diff-59130575b4fb2932c957db2922977d7d89afb0b2085357db1a14615a2fcad776Patch, Third Party Advisory
https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0Patch, Third Party Advisory
https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/12/msg00037.htmlMailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TUIS2KE3HZ2AAQKXFLTJFZPP2IFHJTC7/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/V2XMOM5PFT6U5AAXY6EFNT5JZCKKHK2V/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WZGNET2A4WGLSUXLBFYKNC5PXHQMI3I7/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZQ4SPKJX3RRJK4UWA6FXCRHD2TVRQI44/
https://security.gentoo.org/glsa/202208-06Third Party Advisory
https://security.netapp.com/advisory/ntap-20220107-0005/Third Party Advisory
https://www.debian.org/security/2022/dsa-5043Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.htmlPatch, Third Party Advisory
https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664aPatch, Third Party Advisory
https://github.com/lxml/lxml/commit/a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c#diff-59130575b4fb2932c957db2922977d7d89afb0b2085357db1a14615a2fcad776Patch, Third Party Advisory
https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0Patch, Third Party Advisory
https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/12/msg00037.htmlMailing List, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TUIS2KE3HZ2AAQKXFLTJFZPP2IFHJTC7/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/V2XMOM5PFT6U5AAXY6EFNT5JZCKKHK2V/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WZGNET2A4WGLSUXLBFYKNC5PXHQMI3I7/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZQ4SPKJX3RRJK4UWA6FXCRHD2TVRQI44/
https://security.gentoo.org/glsa/202208-06Third Party Advisory
https://security.netapp.com/advisory/ntap-20220107-0005/Third Party Advisory
https://www.debian.org/security/2022/dsa-5043Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.htmlPatch, Third Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.htmlPatch, Third Party Advisory

Timeline

Published: Dec 13, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43818?

How severe is CVE-2021-43818?

CVE-2021-43818 has a CVSS score of 7.1/10 (HIGH severity). The EPSS model estimates a 2.46% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43818?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-43818?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST