Critical RCE in widely deployed Cisco email gateway products; affects enterprise mail infrastructure and can cause broad compromise.
CVE-2026-20353
Critical RCE in Cisco Secure Email Gateway and Secure Email and Web Manager.
Is CVE-2026-20353 being exploited?
Not confirmed. CVE-2026-20353 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-2026-20353?
CVE-2026-20353 is rated Critical with a CVSS score of 9.8. 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-2026-20353?
Yes. A fix has been recorded for CVE-2026-20353. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-20353 affect?
CVE-2026-20353 affects Cisco Secure Email Gateway (ESA), Cisco Secure Email and Web Manager. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-20353?
Apply Cisco hardening updates immediately; follow vendor mitigations.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote code execution allowing arbitrary code on the gateway, full system compromise, data interception, and potential lateral movement.
Immediate action required
- affected14.0.0-698
- affected13.5.1-277
- affected13.0.0-392
- affected14.2.0-620
- affected13.0.5-007
- affected13.5.4-038
- affected14.2.1-020
- affected14.3.0-032
- affected15.0.0-104
- affected15.0.1-030
- affected15.5.0-048
- affected15.5.1-055
- affected15.5.2-018
- affected16.0.0-050
- affected15.0.3-002
- affected16.0.0-054
- affected15.5.3-022
- affected16.0.1-017
- affected15.5.4-012
- affected16.0.4-016
- affected15.0.5-016
- affected16.0.2-112
- affected16.0.3-044
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.