What is CVE-2026-21483?

CVE-2026-21483 is a medium-severity vulnerability in Knadh Listmonk, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-01-02.

How severe is CVE-2026-21483?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Knadh Listmonk

CVE-2026-21483

listmonk is a standalone, self-hosted, newsletter and mailing list manager. Prior to version 6.0.0, lower-privileged user with campaign management permissions can inject malicious JavaScript into campaigns or templates. When a higher-privileged user (Super Admin) views or previews this content, the XSS executes in their browser context, allowing the attacker to perform privileged actions such as creating backdoor admin accounts. The attack can be weaponized via the public archive feature, where victims simply need to visit a link - no preview click required. Version 6.0.0 fixes the issue.

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.002 (9.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

Affected products

Knadh Listmonk — versions < 6.0.0
Nadh Listmonk

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

security-advisories@github.com (x_refsource_CONFIRM, Exploit, Vendor Advisory)

Frequently asked questions

What is CVE-2026-21483?: CVE-2026-21483 is a medium-severity vulnerability in Knadh Listmonk, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-01-02.
How severe is CVE-2026-21483?: Medium severity. CVSS v3 base score is 5.4 out of 10.