CVE-2021-28957
An XSS vulnerability was discovered in python-lxml's clean module versions before 4.6.3.
Does this matter?
Lower severity and a low EPSS score (4.04%). Track it; it rarely justifies an emergency change on its own.
Description
An XSS vulnerability was discovered in python-lxml's clean module versions before 4.6.3. When disabling the safe_attrs_only and forms arguments, the Cleaner class does not remove the formaction attribute allowing for JS to bypass the sanitizer. A remote attacker could exploit this flaw to run arbitrary JS code on users who interact with incorrectly sanitized HTML. This issue is patched in lxml 4.6.3.
- CVSS 3.1
- 6.1 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- EPSS
- 4.04% probability · 91th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-79
- Affected
- lxml/lxml · debian/debian linux · fedoraproject/fedora · netapp/snapcenter · oracle/zfs storage appliance kit
- Source
- cve@mitre.org
EPSS 4.0% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugs.launchpad.net/lxml/+bug/1888153Exploit, Issue Tracking, Third Party Advisory
- https://github.com/lxml/lxml/commit/a5f9cb52079dc57477c460dbe6ba0f775e14a999Patch, Third Party Advisory
- https://github.com/lxml/lxml/pull/316/commits/10ec1b4e9f93713513a3264ed6158af22492f270Patch, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/03/msg00031.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3C2R44VDUY7FJVMAVRZ2WY7XYL4SVN45/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XXN3QPWCTQVOGW4BMWV3AUUZZ4NRZNSQ/
- https://security.gentoo.org/glsa/202208-06Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210521-0004/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4880Third Party Advisory
- https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch, Third Party Advisory
- https://bugs.launchpad.net/lxml/+bug/1888153Exploit, Issue Tracking, Third Party Advisory
- https://github.com/lxml/lxml/commit/a5f9cb52079dc57477c460dbe6ba0f775e14a999Patch, Third Party Advisory
- https://github.com/lxml/lxml/pull/316/commits/10ec1b4e9f93713513a3264ed6158af22492f270Patch, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/03/msg00031.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3C2R44VDUY7FJVMAVRZ2WY7XYL4SVN45/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XXN3QPWCTQVOGW4BMWV3AUUZZ4NRZNSQ/
- https://security.gentoo.org/glsa/202208-06Third Party Advisory
- https://security.netapp.com/advisory/ntap-20210521-0004/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4880Third Party Advisory
- https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.