CVE-2024-34078
html-sanitizer allows arbitrary HTML present after sanitization because of unicode normalization
html-sanitizer is an allowlist-based HTML cleaner. 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. The problem has been fixed in 2.4.2.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
html-sanitizer allows arbitrary HTML present after sanitization because of unicode normalization
html-sanitizer is an allowlist-based HTML cleaner. 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. The problem has been fixed in 2.4.2.
- Record
CVE-2024-34078- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
EUVDEUVD-2024-1840
html-sanitizer is an allowlist-based HTML cleaner. 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. The problem has been fixed in 2.4.2.
- Record
EUVD-2024-1840- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-wvhx-q427-fgh3 No score
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.
- Record
GHSA-wvhx-q427-fgh3- Updated
- 2026-11-02
NVD
html-sanitizer is an allowlist-based HTML cleaner. 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. The problem has been fixed in 2.4.2.
- Record
CVE-2024-34078- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSV
html-sanitizer allows arbitrary HTML present after sanitization because of unicode normalization
html-sanitizer is an allowlist-based HTML cleaner. 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. The problem has been fixed in 2.4.2.
- Record
CVE-2024-34078- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2024-34078
html-sanitizer is an allowlist-based HTML cleaner. 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. The problem has been fixed in 2.4.2.
- Record
DEBIAN-CVE-2024-34078- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVUBUNTU-CVE-2024-34078
html-sanitizer is an allowlist-based HTML cleaner. 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. The problem has been fixed in 2.4.2.
- Record
UBUNTU-CVE-2024-34078- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVGHSA-wvhx-q427-fgh3 No score
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.
- Record
GHSA-wvhx-q427-fgh3- Updated
- 2026-11-02
OSVPYSEC-2026-1455 No score
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.
- Record
PYSEC-2026-1455- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
html-sanitizerPyPI |
before 2.4.2 | 2.4.2 |
python-html-sanitizerDebian:11 |
before 1.9.1-2+deb11u1, plus listed versions 1.9.1-2 |
1.9.1-2+deb11u1 |
html-sanitizerPyPI |
before 2.4.2, plus listed versions 1.0.01.1.01.1.11.1.21.1.3 Show 27 moreShow less1.1.41.2.01.2.11.3.01.4.01.5.01.6.01.6.11.6.21.6.31.6.41.7.01.7.11.7.21.7.31.8.01.9.01.9.11.9.21.9.32.0.02.1.02.2.02.3.02.3.12.4.02.4.1 |
2.4.2 |
python-html-sanitizerUbuntu:22.04:LTS |
All versions, plus listed versions 1.9.1-21.9.3-1 |
None known |
python-html-sanitizerUbuntu:24.04:LTS |
All versions, plus listed versions 2.2-1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, products | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2024-34078 is a medium vulnerability (CVSS 6.1) in Matthiask Html-sanitizer, published May 6, 2024. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.56%, the 46th percentile. Fixed in html-sanitizer 2.4.2.
References
github.com/matthiask/html-sanitizer/security/advisories/GHSA-wvhx-q427-fgh3
lists.debian.org/debian-lts-announce/2024/08/msg00000.html
nvd.nist.gov/vuln/detail/CVE-2024-34078