lxml's HTML Cleaner allows crafted and SVG embedded scripts to pass through
Impact
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.
Patches
The issue has been resolved in lxml 4.6.5.
Workarounds
None.
References
The issues are tracked under the report IDs GHSL-2021-1037 and GHSL-2021-1038.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | lxml | < 4.6.5 | 4.6.5 |
References
- https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0
- https://github.com/lxml/lxml/commit/a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c#diff-59130575b4fb2932c957db2922977d7d89afb0b2085357db1a14615a2fcad776
- https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8
- https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664a
- https://nvd.nist.gov/vuln/detail/CVE-2021-43818
- https://www.oracle.com/security-alerts/cpujul2022.html
- https://www.oracle.com/security-alerts/cpuapr2022.html
- https://www.debian.org/security/2022/dsa-5043
- https://security.netapp.com/advisory/ntap-20220107-0005
- https://security.gentoo.org/glsa/202208-06
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZQ4SPKJX3RRJK4UWA6FXCRHD2TVRQI44
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WZGNET2A4WGLSUXLBFYKNC5PXHQMI3I7
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/V2XMOM5PFT6U5AAXY6EFNT5JZCKKHK2V
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TUIS2KE3HZ2AAQKXFLTJFZPP2IFHJTC7
- https://lists.debian.org/debian-lts-announce/2021/12/msg00037.html
- https://github.com/pypa/advisory-database/tree/main/vulns/lxml/PYSEC-2021-852.yaml
- https://github.com/lxml/lxml
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N- Weakness (CWE)
CWE-74, CWE-79- Platform
- Python (PyPI)
- Package
lxml- Disclosed
- 13.12.2021
- Updated
- 11.10.2026 13:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2021-852 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-55x5-fj6c-h6m8 - CC BY 4.0
Vulnerability history: lxml
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 7
- First → latest
- 05.2014 04.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 6
Disclosures per year
- 2017: 0
- 2018: 1
- 2019: 0
- 2020: 1
- 2021: 2
- 2022: 1
- 2023: 0
- 2024: 0
- 2025: 0
- 2026: 1
earlier: 1
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lxml's HTML Cleaner allows crafted and SVG embedded scripts to pass through this entry
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