vulntracker.iovulntracker.io
© 2026 vulntracker.io

CVE-2021-43818

HTML Cleaner allows crafted and SVG embedded scripts to pass through

HIGH
7.1
CVSS Score
Published: December 13, 2021 at 06:05 PM UTC
Updated: June 17, 2026 at 04:11 AM UTC
12 products affected across 5 vendorsDebian LinuxFedoraSolidfire

Using lxml by lxml?

Get instant alerts when new vulnerabilities affect lxml - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Start FreeSign In
Severity
HIGH7.1
Exploit prediction
EPSS 3%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

References (14)

x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664a
x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/lxml/lxml/commit/a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c#diff-59130575b4fb2932c957db2922977d7d89afb0b2085357db1a14615a2fcad776
x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0
x_refsource_CONFIRMThird Party Advisory
Source: [email protected]
https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8
Mailing Listx_refsource_MLISTThird Party Advisory
Source: [email protected]
https://lists.debian.org/debian-lts-announce/2021/12/msg00037.html
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TUIS2KE3HZ2AAQKXFLTJFZPP2IFHJTC7/
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/V2XMOM5PFT6U5AAXY6EFNT5JZCKKHK2V/
Vendor Advisoryx_refsource_FEDORA
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WZGNET2A4WGLSUXLBFYKNC5PXHQMI3I7/

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.1HIGH[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
LOW
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-74CWE-79

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Create accountSign in
Free plan, no card