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Vulnerability record · CVE-2020-27783 · published 3 December 2020

CVE-2020-27783: Lxml cross-site scripting vulnerability

LLxml · Lxml

A XSS vulnerability was discovered in python-lxml's clean module. The module's parser didn't properly imitate browsers, which caused different behaviors between the sanitizer and the user's page. A remote attacker could exploit this flaw to run arbitrary HTML/JS code.

6.1 CVSS 3.1 Medium EPSS 4.0% · top 9.9% CWE-79 · Cross-site scripting
6.1CVSS 3.1 base score, v2 4.3
4.0%EPSS exploitation probability, 30 days
NoNot in CISA KEV
8Affected product versions listed by NVD
16References, 4 tagged exploit
17 Jun 2026Last modified by NVD

Description

A XSS vulnerability was discovered in python-lxml's clean module. The module's parser didn't properly imitate browsers, which caused different behaviors between the sanitizer and the user's page. A remote attacker could exploit this flaw to run arbitrary HTML/JS code.

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

Affected products

8 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://advisory.checkmarx.net/advisory/CX-2020-4286 ExploitThird Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1901633 ExploitIssue TrackingPatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2020/12/msg00028.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JKG67GPGTV23KADT4D4GK4R
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TMHVKRUT22LVWNL3TB7HPSD
https://security.netapp.com/advisory/ntap-20210521-0003/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4810 Third Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.html PatchThird Party Advisory
https://advisory.checkmarx.net/advisory/CX-2020-4286 ExploitThird Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1901633 ExploitIssue TrackingPatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2020/12/msg00028.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JKG67GPGTV23KADT4D4GK4R
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TMHVKRUT22LVWNL3TB7HPSD
https://security.netapp.com/advisory/ntap-20210521-0003/ Third Party Advisory
https://www.debian.org/security/2020/dsa-4810 Third Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.html PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2020-27783), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.