Affects widely deployed Cisco Secure FMC/FTD; allows attacker to gain manager/root on network security appliances — high enterprise impact and potential widespread disruption.
CVE-2026-20323
Unauthenticated adjacent TLS impersonation grants manager/root on Cisco FMC/FTD sftunnel
Is CVE-2026-20323 being exploited?
Not confirmed. CVE-2026-20323 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.
How severe is CVE-2026-20323?
CVE-2026-20323 is rated High with a CVSS score of 8.3. 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-2026-20323?
Not known from our data. No patch reference has been recorded for CVE-2026-20323, which is not the same as no patch existing — a fix may have shipped without a tagged reference, or after this record was written. The vendor advisory is the only authority on whether a fix exists, and mitigations may be available regardless.
What does CVE-2026-20323 affect?
CVE-2026-20323 affects Cisco Secure FMC Software, Cisco Secure FTD Software. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-20323?
Follow Cisco advisory, restrict sftunnel access, enforce TLS cert validation, rotate certs, monitor logs.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Adjacent unauthenticated attacker can use a crafted TLS cert to register as an sftunnel peer and obtain manager/root privileges if sftunnel is down or disrupted.
Immediate action required
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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.