CVE-2026-77088

justhtml 0.9.0 through 1.21.0 Cross-Site Scripting via code-span

Published Aug 23, 2026 CVSS 4.0 · 5.3 Medium EPSS < 1% KEV · Not listed
Description
justhtml versions 0.9.0 through 1.21.0 contain a cross-site scripting vulnerability in to_markdown() where inline code spans fail to account for blank lines as block boundaries. Attackers can inject blank lines into code or pre element text to break the inline span, causing sanitized HTML to be emitted unescaped and re-parsed as live Markdown by compliant renderers.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Emilstenstrom
Emilstenstrom justhtml
Vendors & Products Emilstenstrom
Emilstenstrom justhtml
Type Values Removed Values Added
Description justhtml versions 0.9.0 through 1.21.0 contain a cross-site scripting vulnerability in to_markdown() where inline code spans fail to account for blank lines as block boundaries. Attackers can inject blank lines into code or pre element text to break the inline span, causing sanitized HTML to be emitted unescaped and re-parsed as live Markdown by compliant renderers.
Title justhtml 0.9.0 through 1.21.0 Cross-Site Scripting via code-span
Weaknesses CWE-79
References
Metrics cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}

cvssV4_0

{'score': 5.3, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Aug 29, 2026, 11:47 AM
Reserved
Aug 20, 2026, 10:55 AM
Status
Deferred
Published
Aug 23, 2026, 2:16 PM
Modified
Oct 12, 2026, 4:10 PM