Description
Incomplete blacklist vulnerability in the lxml.html.clean module in lxml before 3.3.5 allows remote attackers to conduct cross-site scripting (XSS) attacks via control characters in the link scheme to the clean_html function.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | lxml | 3.3.5-1 | — |
| Debian 13 | lxml | 3.3.5-1 | — |
| Debian 12 | lxml | 3.3.5-1 | — |
| Debian 7 | lxml | 2.3.2-1+deb7u1 | DSA-2941-1 |
| Debian 6.0 | lxml | 2.2.8-2+deb6u1 | DLA-0009-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 14.04 LTS | lxml | 3.3.3-1ubuntu0.1 | USN-2217-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2 | python-lxml +1 | 3.2.1-4.amzn2.0.4 | ALAS2-2023-1956 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
Exploit-DB 1
- lxml - 'clean_html' Security Bypass EDB-39155 · remote · Apr 15, 2014 · verified
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | lxml | < 3.3.5 | 3.3.5 | GHSA-57qw-cc2g-pv5p |
Advisories 5
- DSA-2941-1 lxml - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-0009-1 lxml - security update Debian Security (DSA / DLA) · Mar 9, 2026
- USN-2217-1 lxml vulnerability Ubuntu Security Notices (USN) · Feb 10, 2026
- WID-SEC-2024-1086 IBM QRadar SIEM: Mehrere Schwachstellen BSI CERT-Bund (WID) · Oct 19, 2025
- ALAS2-2023-1956 Important: python-lxml security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Mar 7, 2025
References
- DSA-2941 vendor-advisory
- http://lxml.de/3.3/changes-3.3.5.html
- [oss-security] 20140509 Re: CVE request: python-lxml clean_html() input sanitization flaw mailing-list
- USN-2217-1 vendor-advisory
- [lxml] 20140415 lxml.html.clean vulnerability mailing-list
- 58744 third-party-advisory
- http://advisories.mageia.org/MGASA-2014-0218.html
- 67159 vdb-entry
- MDVSA-2015:112 vendor-advisory
- 58013 third-party-advisory
- 20140415 lxml (python lib) vulnerability mailing-list
- 59008 third-party-advisory
- openSUSE-SU-2014:0735 vendor-advisory
- 20140430 Re: lxml (python lib) vulnerability mailing-list