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Unratedamended

Arbitrary HTML present after sanitization because of unicode normalization

CVE-2024-34078GHSA-wvhx-q427-fgh3

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (html-sanitizer 2.4.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
not scored
EPSS
  • CVE-2024-34078: 0.56% estimated exploitation activity in the next 30 days; percentile 46.38 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Impact If using keeptypographicwhitespace=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 keeptypographicwhitespace=True explicitly, or normalize to NFKC yourself earlier.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-wvhx-q427-fgh3

  2. Revision 1 · created ·

    Published from osv record GHSA-wvhx-q427-fgh3

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2024-34078

Advisory: Arbitrary HTML present after sanitization because of unicode normalization
IDs: CVE-2024-34078, GHSA-wvhx-q427-fgh3
Record: https://patchnext.com/advisories/cve-2024-34078 (revision 2, source checked 26 Oct 2026, 13:13 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: html-sanitizer 2.4.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI html-sanitizer: affected < 2.4.2; fixed in 2.4.2

## Suggested inspection (read-only)
- `python -m pip show html-sanitizer`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on html-sanitizer.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-wvhx-q427-fgh3 (OSV record GHSA-wvhx-q427-fgh3 lists affected ranges: PyPI html-sanitizer >=0 <2.4.2 (fixed))
- Verified: https://github.com/advisories/GHSA-wvhx-q427-fgh3 (GitHub-reviewed advisory GHSA-wvhx-q427-fgh3 lists affected ranges: PyPI html-sanitizer >=0 <2.4.2)

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