Arbitrary HTML present after sanitization because of unicode normalization
Impact
If using keep_typographic_whitespace=False (which is the default), the sanitizer normalizes unicode to the NFKC form at the end. Some unicode characters normalize to chevrons; this allows specially crafted HTML to escape sanitization.
Patches
The problem has been fixed in 2.4.2.
Workarounds
Set keep_typographic_whitespace=True explicitly, or normalize to NFKC yourself earlier.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | html-sanitizer | < 2.4.2 | 2.4.2 |
References
- https://github.com/matthiask/html-sanitizer/security/advisories/GHSA-wvhx-q427-fgh3
- https://github.com/matthiask/html-sanitizer/commit/48db42fc5143d0140c32d929c46b802f96913550
- https://github.com/matthiask/html-sanitizer
- https://pypi.org/project/html-sanitizer
- https://github.com/advisories/GHSA-wvhx-q427-fgh3
- https://nvd.nist.gov/vuln/detail/CVE-2024-34078
- Weakness (CWE)
-- Platform
- Python (PyPI)
- Package
html-sanitizer- Disclosed
- 06.05.2024
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-1455 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-wvhx-q427-fgh3 - CC BY 4.0
Vulnerability history: html-sanitizer
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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