Multiple security fixes in justhtml

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

1.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U · score source

EPSS

• CVE-2026-7808: 0.59% estimated exploitation activity in the next 30 days; percentile 48.12 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary justhtml 1.16.0 fixes multiple security issues in sanitization, serialization, and programmatic DOM handling. Most of these issues affected one of these advanced paths rather than ordinary parsed HTML with the default safe settings: - programmatic DOM input to sanitize() or sanitizedom() - reused or mutated sanitization policy objects - custom policies that preserve foreign namespaces such as SVG or MathML Affected versions - justhtml <= 1.15.0 Fixed version - justhtml 1.16.0 released on April 12, 2026 Impact Policy reuse and mutation Nested mutation of sanitization policy internals could weaken later sanitization by leaving stale compiled sanitizers active, or by mutating exported default policy internals process-wide. In-memory sanitization gaps Programmatic DOM sanitization could miss dangerous mixed-case tag names such as ScRiPt or StYlE, and custom dropcontenttags values such as {"SCRIPT"} could silently fail to drop dangerous subtrees. Serialization injection Crafted…

Published by the source

14 Apr 2026, 20:05 UTC

Last modified by the source

24 Aug 2026, 03:55 UTC

Source last checked

26 Oct 2026, 13:40 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-4p64-v8f5-r2gx

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-4p64-v8f5-r2gx

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# Patch Next advisory brief: CVE-2026-7808

Advisory: Multiple security fixes in justhtml
IDs: CVE-2026-7808, GHSA-4p64-v8f5-r2gx
Record: https://patchnext.com/advisories/cve-2026-7808 (revision 3, source checked 26 Oct 2026, 13:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 1.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: justhtml 1.16.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI justhtml: affected <= 1.15.0; fixed in 1.16.0

## Suggested inspection (read-only)
- `python -m pip show justhtml`: 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 justhtml.
- 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-4p64-v8f5-r2gx (OSV record GHSA-4p64-v8f5-r2gx lists affected ranges: PyPI justhtml >=0 <1.16.0 (fixed))
- Verified: https://github.com/advisories/GHSA-4p64-v8f5-r2gx (GitHub-reviewed advisory GHSA-4p64-v8f5-r2gx lists affected ranges: PyPI justhtml >=0 <=1.15.0)

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