Connect your agent
AdvisoriesCriticalCheck your lockfilePluginHow it worksPricing Connect your agent

Advisory record · GHSA-c9vm-hv86-f23r

justhtml includes multiple security fixes

CVSS 9.3 CriticalCriticalEPSS 0.0059 · 48th percentile

Critical, because:

  • CVSS score 9.3: 9.0 or more.

How we decide what’s critical

Published by the GitHub Advisory Database at 10 Apr 2026, 19:20 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
justhtmlPyPI<1.15.01.15.0
Identifiers
GHSA-c9vm-hv86-f23r · CVE-2026-5388
Weakness (CWE)
CWE-20 · CWE-79 · CWE-178 · CWE-755
Tags
Published
10 Apr 2026
Updated
24 Aug 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The justhtml package, versions 1.14.0 and earlier, has several security issues affecting URL sanitization helpers, HTML serialization, Markdown passthrough, and custom sanitization policies. Most of the custom-policy issues did not affect the default sanitize=True configuration, but the helper APIs, programmatic DOM serialization, and html_passthrough=True were exposed more broadly. Upgrade to justhtml 1.15.0; if that is not possible, avoid html_passthrough=True with untrusted content and avoid untrusted custom policies.

Written 5 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
9.3 Critical 4.0 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N CNA (VulnCheck)
  • CISA KEV Not listed.
  • EPSS 0.0059, the 48th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:39 UTC First seen by agentprime
  2. 31 Oct 2026, 14:39 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.