CVE-2026-5389CWE-80

CVE-2026-5389

Medium · published August 23, 2026

CVSS v3.1
6.1
EPSS
0%
Percentile
13.0
In the wild
Unconfirmed
What it is

justhtml versions before 1.13.0 contain a cross-site scripting vulnerability in the to_markdown() function when serializing attacker-controlled pre content. Attackers can place backticks inside sanitized pre elements to break out of fixed-length code fences, allowing raw HTML to execute when the generated Markdown is rendered by CommonMark or GFM-style renderers.

The record
Technical detail
CVSS v3.1
6.1 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS v4.0
5.1 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
EPSS
0.00230 · 13.0th percentile
Weakness
CWE-80 · Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)
Published
2026-08-23T18:16Z
References (3)
https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-5vp3-3cg6-2rq3 · [email protected]https://www.vulncheck.com/advisories/justhtml-before-xss-via-code-fence-breakout · [email protected]https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-5vp3-3cg6-2rq3 · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 23 AUG 13:34Z
    justhtml before 1.13.0 XSS via code fence breakout
    cvelistv5