CVE-2026-54003
Remote admin takeover via spoofed proxy headers on Kirby CMS.
Is CVE-2026-54003 being exploited?
Not confirmed. CVE-2026-54003 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 0.74% probability of exploitation in the next 30 days.
How severe is CVE-2026-54003?
CVE-2026-54003 is rated Critical with a CVSS score of 9.1. 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-2026-54003?
Yes. A fix has been recorded for CVE-2026-54003. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-54003 affect?
CVE-2026-54003 affects Kirby CMS <4.9.4, Kirby CMS <5.4.4, Public sites behind reverse proxies setting Forwarded/X-Client-IP/X-Real-IP with no users configured. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-54003?
Upgrade to Kirby 4.9.4 or 5.4.4; validate/restrict proxy IP headers and block public install paths.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote attacker can install the Panel and create the first admin user via forged Forwarded/X-Real-IP headers, enabling full site/admin takeover and potential code execution.
Immediate action required
- affected< 4.9.4
- affected>= 5.0.0 and < 5.4.4
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.