Widely used server platform; mTLS auth boundary compromised; could allow impersonation across services.
CVE-2026-27586
Caddy pre-2.11.1: mTLS bypass via missing CA file; any system-trusted cert accepted.
Is CVE-2026-27586 being exploited?
Not confirmed. CVE-2026-27586 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 0.27% probability of exploitation in the next 30 days.
How severe is CVE-2026-27586?
CVE-2026-27586 is rated High with a CVSS score of 8.8. 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-2026-27586?
Yes. A fix has been recorded for CVE-2026-27586. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-27586 affect?
CVE-2026-27586 affects Caddy Server (pre-2.11.1). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-27586?
Upgrade to 2.11.1+ to fix
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Allows bypass of mTLS authentication by accepting any system-trusted client cert when CA file is unavailable.
Patch when possible
- affected< 2.11.1
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.