CVE-2026-5389

Published Aug 23, 2026

Last updated 3 days ago

Overview

AI description

Automated description summarized from trusted sources.

CVE-2026-5389 describes a cross-site scripting (XSS) vulnerability found in `justhtml` versions prior to 1.13.0. This flaw specifically resides within the `to_markdown()` function, which is responsible for converting content into Markdown format. The vulnerability allows an attacker to inject malicious content by placing backticks inside sanitized pre-formatted (`pre`) elements. This action enables them to bypass fixed-length code fences, leading to the execution of raw HTML when the generated Markdown is subsequently rendered by CommonMark or GFM-style renderers.

Description: 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.
Source: disclosure@vulncheck.com
NVD status: Deferred

Risk scores

CVSS 4.0

Type: Secondary
Base score: 5.1
Impact score: -
Exploitability score: -
Vector string: 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Severity: MEDIUM

CVSS 3.1

Type: Secondary
Base score: 6.1
Impact score: 2.7
Exploitability score: 2.8
Vector string: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Severity: MEDIUM

Weaknesses

disclosure@vulncheck.com: CWE-80

Hype score: Not currently trending

References

Sources include official advisories and independent security research.