CVE-2026-8833
Auth URL validation bypass enables XSS in Checkmk.
Is CVE-2026-8833 being exploited?
Not confirmed. CVE-2026-8833 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.14% probability of exploitation in the next 30 days.
How severe is CVE-2026-8833?
CVE-2026-8833 is rated High with a CVSS score of 8.5. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-8833?
Yes. A fix has been recorded for CVE-2026-8833. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-8833 affect?
CVE-2026-8833 affects Checkmk <2.5.0p5, Checkmk <2.4.0p31, Checkmk <2.3.0p48, Checkmk 2.2.0.x. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-8833?
Upgrade to fixed version (>=2.5.0p5 or latest patched build)
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Authenticated attacker can inject javascript: URLs to trigger XSS in other users' browsers, potentially exposing data.
Immediate action required
- affected>= 2.5.0 and < 2.5.0p5
- affected>= 2.4.0 and < 2.4.0p31
- affected>= 2.3.0 and < 2.3.0p48
- affected2.2.0
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.