listmonk Vulnerable to Stored XSS Leading to Admin Account Takeover

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:P · score source

EPSS

• CVE-2026-21483: 0.23% estimated exploitation activity in the next 30 days; percentile 13.33 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Security Advisory: Stored XSS Leading to Admin Account Takeover Affected Versions: ≤ 5.1.0 Vulnerability Type: CWE-79: Stored Cross-Site Scripting --- Summary A 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. --- Required Attacker Permissions Note: These are common permissions for content managers who are not full admins. --- Attack Vectors Vector 1: Raw HTML (Direct Script Tag) Vector 2: Go Template Safe Function --- Attack Scenarios Scenario 1: Campaign Preview Attack 1. Attacker creates campaign with XSS payload 2. Request is made to super admin: "Please review my…

Published by the source

2 Jan 2026, 23:04 UTC

Last modified by the source

2 Jan 2026, 23:04 UTC

Source last checked

26 Oct 2026, 15:14 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-jmr4-p576-v565

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# Patch Next advisory brief: CVE-2026-21483

Advisory: listmonk Vulnerable to Stored XSS Leading to Admin Account Takeover
IDs: CVE-2026-21483, GHSA-jmr4-p576-v565
Record: https://patchnext.com/advisories/cve-2026-21483 (revision 1, source checked 26 Oct 2026, 15:14 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/knadh/listmonk 6.0.0, 1.1.1-0.20251231125615-74dc5a01cfbb. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/knadh/listmonk: affected >= 1.1.1, < 6.0.0; < 1.1.1-0.20251231125615-74dc5a01cfbb; fixed in 6.0.0, 1.1.1-0.20251231125615-74dc5a01cfbb

## Suggested inspection (read-only)
- Go github.com/knadh/listmonk: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/knadh/listmonk.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-jmr4-p576-v565 (GitHub-reviewed advisory GHSA-jmr4-p576-v565 lists affected ranges: Go github.com/knadh/listmonk >=1.1.1 =0 <1.1.1-0.20251231125615-74dc5a01cfbb)

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