Cross-Site Scripting Vulnerability in justhtml by Emil Stenstrom
CVE-2026-77088

5.3MEDIUM

Key Information:

Vendor

Emilstenstrom

Status
Justhtml
Vendor
CVE Published:
23 August 2026

What is CVE-2026-77088?

The justhtml library, versions 0.9.0 through 1.21.0, is affected by a cross-site scripting flaw within the to_markdown() function. This vulnerability arises when inline code spans do not properly handle blank lines as delimiters, allowing attackers to inject blank lines into code or preformatted element texts. As a result, sanitized HTML may be emitted in an unescaped format and re-interpreted as live Markdown by compliant renderers. This behavior can be exploited to execute malicious scripts in the context of a user's session.

Affected Version(s)

justhtml 0

References

https://github.com/EmilStenstrom/justhtml/security/adviso...
vendor-advisory
https://www.vulncheck.com/advisories/justhtml-through-cro...
third-party-advisory

CVSS V4

Score:
5.3
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

seankohjs
yueyueL
.