What is CVE-2026-77088?

CVE-2026-77088 is a medium-severity vulnerability, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-08-23.

How severe is CVE-2026-77088?

Medium severity. CVSS v3 base score is 6.1 out of 10.

CVE-2026-77088

CVE-2026-77088

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.

Vulnerability class: XSS (Cross-Site Scripting)

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

disclosure@vulncheck.com (vendor-advisory)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-77088?: CVE-2026-77088 is a medium-severity vulnerability, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-08-23.
How severe is CVE-2026-77088?: Medium severity. CVSS v3 base score is 6.1 out of 10.