01 Record

CVE-2021-28957

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

MediumPUBLISHEDCNA: mitre

CNA base score6.1 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

View raw JSON

02 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

03 Exploitation and scoring

Exploitation

Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.

SSVC decision

ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

4.03% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 90.3% of scored records. A rank, not a probability.

NVD base score

6.1 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

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

NVD analysis status

Modified. NVD last modified this record on 2026-06-17.

Red Hat severity

Moderate. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published

2021-03-21 04:39Z5 YR AGO

Last updated

2025-12-17 21:31Z10 MO AGO

Reserved

2021-03-21

Assigning CNA

mitre

Record state

PUBLISHED

Severity

Medium (CVSS 6.1)

CNA CVSS vector

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

Weaknesses

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')Base

Data version

5.2

Document digest

7499d28aa430b7341061e730624aa6b160b7fb39eabe5a7ee4999b259a508f72

05 Affected products

VendorProductVersionsPlatforms

debiandebian_linuxNot specified—

fedoraprojectfedoraNot specified—

lxmllxmlNot specified—

netappsnapcenterNot specified—

oraclezfs_storage_appliance_kitNot specified—

redhatansible_automation_platformNot specified—

redhatansible_towerNot specified—

redhatenterprise_linuxNot specified—

redhatopenstackNot specified—

redhatrhel_software_collectionsNot specified—

06 References

bugs.launchpad.nethttps://bugs.launchpad.net/lxml/+bug/1888153x_refsource_MISC
github.comhttps://github.com/lxml/lxml/pull/316/commits/10ec1b4e9f93713513a3264ed6158af22492f270x_refsource_MISC
lists.debian.org[debian-lts-announce] 20210324 [SECURITY] [DLA 2606-1] lxml security updatehttps://lists.debian.org/debian-lts-announce/2021/03/msg00031.htmlmailing-listx_refsource_MLIST
www.debian.orgDSA-4880https://www.debian.org/security/2021/dsa-4880vendor-advisoryx_refsource_DEBIAN
lists.fedoraproject.orgFEDORA-2021-28723f9670https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3C2R44VDUY7FJVMAVRZ2WY7XYL4SVN45/vendor-advisoryx_refsource_FEDORA
lists.fedoraproject.orgFEDORA-2021-4cdb0f68c7https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XXN3QPWCTQVOGW4BMWV3AUUZZ4NRZNSQ/vendor-advisoryx_refsource_FEDORA
www.oracle.comhttps://www.oracle.com/security-alerts/cpuoct2021.htmlx_refsource_MISC
github.comhttps://github.com/lxml/lxml/commit/a5f9cb52079dc57477c460dbe6ba0f775e14a999x_refsource_MISC
security.netapp.comhttps://security.netapp.com/advisory/ntap-20210521-0004/x_refsource_CONFIRM
security.gentoo.orgGLSA-202208-06https://security.gentoo.org/glsa/202208-06vendor-advisoryx_refsource_GENTOO

07 Fixed in

AlmaLinux 8

babel
Fixed in 2.5.1-10.module_el8.6.0+2781+fed64c13
python-nose-docs
Fixed

A version is affected if any line below covers it.
- Affected before 1.3.7-31.module_el8.5.0+2569+5c5719bc
- Affected before 1.3.7-31.module_el8.6.0+2781+fed64c13
python-psycopg2-doc
Fixed in 2.7.5-7.module_el8.6.0+2781+fed64c13
python-sqlalchemy-doc
Fixed

A version is affected if any line below covers it.
- Affected before 1.3.2-2.module_el8.5.0+2569+5c5719bc
- Affected before 1.3.2-2.module_el8.6.0+2781+fed64c13
python2-Cython
Fixed in 0.28.1-7.module_el8.6.0+2781+fed64c13
python2-PyMySQL
Fixed in 0.8.0-10.module_el8.6.0+2781+fed64c13
python2-attrs
Fixed in 17.4.0-10.module_el8.6.0+2781+fed64c13
python2-babel
Fixed in 2.5.1-10.module_el8.6.0+2781+fed64c13
python2-backports
Fixed in 1.0-16.module_el8.6.0+2781+fed64c13
python2-backports-ssl_match_hostname
Fixed in 3.5.0.1-12.module_el8.6.0+2781+fed64c13
python2-bson
Fixed in 3.7.0-1.module_el8.6.0+2781+fed64c13
python2-chardet
Fixed in 3.0.4-10.module_el8.6.0+2781+fed64c13
python2-coverage
Fixed in 4.5.1-4.module_el8.6.0+2781+fed64c13
python2-dns
Fixed in 1.15.0-10.module_el8.6.0+2781+fed64c13
python2-docs
Fixed in 2.7.16-2.module_el8.6.0+2781+fed64c13
python2-docs-info
Fixed in 2.7.16-2.module_el8.6.0+2781+fed64c13
python2-docutils
Fixed in 0.14-12.module_el8.6.0+2781+fed64c13
python2-funcsigs
Fixed in 1.0.2-13.module_el8.6.0+2781+fed64c13
python2-idna
Fixed in 2.5-7.module_el8.6.0+2781+fed64c13
python2-ipaddress
Fixed in 1.0.18-6.module_el8.6.0+2781+fed64c13
python2-jinja2
Fixed in 2.10-9.module_el8.6.0+2781+fed64c13
python2-markupsafe
Fixed in 0.23-19.module_el8.6.0+2781+fed64c13
python2-mock
Fixed in 2.0.0-13.module_el8.6.0+2781+fed64c13
python2-nose
Fixed in 1.3.7-31.module_el8.6.0+2781+fed64c13
python2-numpy
Fixed in 1:1.14.2-16.module_el8.6.0+2781+fed64c13
python2-numpy-doc
Fixed in 1:1.14.2-16.module_el8.6.0+2781+fed64c13
python2-numpy-f2py
Fixed in 1:1.14.2-16.module_el8.6.0+2781+fed64c13
python2-pluggy
Fixed in 0.6.0-8.module_el8.6.0+2781+fed64c13
python2-psycopg2
Fixed in 2.7.5-7.module_el8.6.0+2781+fed64c13
python2-psycopg2-debug
Fixed in 2.7.5-7.module_el8.6.0+2781+fed64c13
python2-psycopg2-tests
Fixed in 2.7.5-7.module_el8.6.0+2781+fed64c13
python2-py
Fixed in 1.5.3-6.module_el8.6.0+2781+fed64c13
python2-pygments
Fixed in 2.2.0-22.module_el8.6.0+2781+fed64c13
python2-pymongo
Fixed in 3.7.0-1.module_el8.6.0+2781+fed64c13
python2-pymongo-gridfs
Fixed in 3.7.0-1.module_el8.6.0+2781+fed64c13
python2-pysocks
Fixed in 1.6.8-6.module_el8.6.0+2781+fed64c13
python2-pytest
Fixed in 3.4.2-13.module_el8.6.0+2781+fed64c13
python2-pytest-mock
Fixed in 1.9.0-4.module_el8.6.0+2781+fed64c13
python2-pytz
Fixed in 2017.2-12.module_el8.6.0+2781+fed64c13
python2-pyyaml
Fixed in 3.12-16.module_el8.6.0+2781+fed64c13

89 further packages in AlmaLinux 8 not shown (first 40 listed).

Arch Linux

python-lxml
Fixed in 4.6.3-1

Source: Arch Linux Security Tracker, the Arch Linux security team. Reformatted by exploit.cc.

CloudLinux 8

babel
Fixed in 2.5.1-10.module_el8.6.0+2781+fed64c13
python-nose-docs
Fixed

A version is affected if any line below covers it.
- Affected before 1.3.7-31.module_el8.5.0+2569+5c5719bc
- Affected before 1.3.7-31.module_el8.6.0+2781+fed64c13
python-psycopg2-doc
Fixed in 2.7.5-7.module_el8.6.0+2781+fed64c13
python-sqlalchemy-doc
Fixed

A version is affected if any line below covers it.
- Affected before 1.3.2-2.module_el8.5.0+2569+5c5719bc
- Affected before 1.3.2-2.module_el8.6.0+2781+fed64c13
python2-Cython
Fixed in 0.28.1-7.module_el8.6.0+2781+fed64c13
python2-PyMySQL
Fixed in 0.8.0-10.module_el8.6.0+2781+fed64c13
python2-attrs
Fixed in 17.4.0-10.module_el8.6.0+2781+fed64c13
python2-babel
Fixed in 2.5.1-10.module_el8.6.0+2781+fed64c13
python2-backports
Fixed in 1.0-16.module_el8.6.0+2781+fed64c13
python2-backports-ssl_match_hostname
Fixed in 3.5.0.1-12.module_el8.6.0+2781+fed64c13
python2-bson
Fixed in 3.7.0-1.module_el8.6.0+2781+fed64c13
python2-chardet
Fixed in 3.0.4-10.module_el8.6.0+2781+fed64c13
python2-coverage
Fixed in 4.5.1-4.module_el8.6.0+2781+fed64c13
python2-dns
Fixed in 1.15.0-10.module_el8.6.0+2781+fed64c13
python2-docs
Fixed in 2.7.16-2.module_el8.6.0+2781+fed64c13
python2-docs-info
Fixed in 2.7.16-2.module_el8.6.0+2781+fed64c13
python2-docutils
Fixed in 0.14-12.module_el8.6.0+2781+fed64c13
python2-funcsigs
Fixed in 1.0.2-13.module_el8.6.0+2781+fed64c13
python2-idna
Fixed in 2.5-7.module_el8.6.0+2781+fed64c13
python2-ipaddress
Fixed in 1.0.18-6.module_el8.6.0+2781+fed64c13
python2-jinja2
Fixed in 2.10-9.module_el8.6.0+2781+fed64c13
python2-markupsafe
Fixed in 0.23-19.module_el8.6.0+2781+fed64c13
python2-mock
Fixed in 2.0.0-13.module_el8.6.0+2781+fed64c13
python2-nose
Fixed in 1.3.7-31.module_el8.6.0+2781+fed64c13
python2-numpy
Fixed in 1:1.14.2-16.module_el8.6.0+2781+fed64c13
python2-numpy-doc
Fixed in 1:1.14.2-16.module_el8.6.0+2781+fed64c13
python2-numpy-f2py
Fixed in 1:1.14.2-16.module_el8.6.0+2781+fed64c13
python2-pluggy
Fixed in 0.6.0-8.module_el8.6.0+2781+fed64c13
python2-psycopg2
Fixed in 2.7.5-7.module_el8.6.0+2781+fed64c13
python2-psycopg2-debug
Fixed in 2.7.5-7.module_el8.6.0+2781+fed64c13
python2-psycopg2-tests
Fixed in 2.7.5-7.module_el8.6.0+2781+fed64c13
python2-py
Fixed in 1.5.3-6.module_el8.6.0+2781+fed64c13
python2-pygments
Fixed in 2.2.0-22.module_el8.6.0+2781+fed64c13
python2-pymongo
Fixed in 3.7.0-1.module_el8.6.0+2781+fed64c13
python2-pymongo-gridfs
Fixed in 3.7.0-1.module_el8.6.0+2781+fed64c13
python2-pysocks
Fixed in 1.6.8-6.module_el8.6.0+2781+fed64c13
python2-pytest
Fixed in 3.4.2-13.module_el8.6.0+2781+fed64c13
python2-pytest-mock
Fixed in 1.9.0-4.module_el8.6.0+2781+fed64c13
python2-pytz
Fixed in 2017.2-12.module_el8.6.0+2781+fed64c13
python2-pyyaml
Fixed in 3.12-16.module_el8.6.0+2781+fed64c13

89 further packages in CloudLinux 8 not shown (first 40 listed).

Derived from AlmaLinux 8. Partial coverage: only packages taken from AlmaLinux 8 are listed.

Debian 12

lxml
Fixed in 4.6.3-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 13

lxml
Fixed in 4.6.3-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 14

lxml
Fixed in 4.6.3-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 16.04 LTS

lxml
Fixed in 3.5.0-1ubuntu0.4

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 18.04 LTS

lxml
Fixed in 4.2.1-1ubuntu0.4

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 20.04 LTS

lxml
Fixed in 4.5.0-1ubuntu0.3

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu Pro 14.04 LTS

lxml
Fixed in 3.3.3-1ubuntu0.2+esm3
Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.