CVE-2026-45721
Pre-auth RCE in Algernon via directory walk to handler.lua.
Is CVE-2026-45721 being exploited?
Not confirmed. CVE-2026-45721 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 0.44% probability of exploitation in the next 30 days.
How severe is CVE-2026-45721?
CVE-2026-45721 is rated Critical with a CVSS score of 9.0. 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-2026-45721?
Yes. A fix has been recorded for CVE-2026-45721. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-45721 affect?
CVE-2026-45721 affects Algernon Go web server (versions < 1.17.7). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-45721?
Upgrade to Algernon 1.17.7+ immediately
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution pre-auth; attacker can place handler.lua up the path and execute commands via the next HTTP request.
Immediate action required
- affected< 1.17.7
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.