CVE-2026-8833 XSS in urls
Authenticated users can inject malicious URLs to execute scripts in other users' browsers, potentially leading to account takeover.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-8833?
CVE-2026-8833 is a high-severity cross-site scripting vulnerability in Checkmk Checkmk, published on 8 Jun 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Improper neutralization of HTML-encoded characters in the URL validation function in Checkmk <2.5.0p5, <2.4.0p31, <2.3.0p48, and all 2.2.0 versions allows an authenticated user to bypass URL validation and inject malicious URLs such as javascript: URIs, resulting in cross-site scripting when another user interacts with the crafted link.
Weakness: CWE-79
Which versions are affected by CVE-2026-8833?
It affects 1 product.
Products include Checkmk Checkmk.
How do I fix CVE-2026-8833?
No fix has been published for CVE-2026-8833 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-8833 being exploited?
There is no known exploitation of CVE-2026-8833 in the wild and no public exploit code.
Other vulnerabilities in Checkmk Checkmk
- CVE-2025-39666 omd: Local privilege escalation when executing omd commands as root
- CVE-2024-8606 Fix 2FA bypass via RestAPI
- CVE-2022-46836 PHP code injection in watolib
- CVE-2025-32919 Privilege Escalation in Windows License plugin for Checkmk Windows Agent
- CVE-2024-28827 Privilege escalation in Windows agent
Sources
Also known as GHSA-hc7p-6r8x-vr4q, UBUNTU-CVE-2026-8833.