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Advisory severityCritical9.8Cisco Exploited

Critical [CVE-2026-20353 +4] Cisco Secure Email Gateway and Secure Email and Web Manager Security Hardening Release: September 2026

This critical-severity Cisco advisory covers CVE-2026-20353 and CVE-2026-76440 and 3 more CVEs affecting Secure Email and Web Manager.

Aggregated and source-linked by VulniPulse. Data sources, validation and limitations. This bulletin covers 5 CVEs; its score, affected versions and guidance may apply to different issues within that bulletin.

cisco-sa-hardening-esa-dfCrfXkm Source published Source updated

VulniPulse record published Record updated

CVE-2026-20353CVE-2026-76440CVE-2026-76441CVE-2026-76442CVE-2026-76443
Affected products & platforms
CiscoUnclassified
Open source advisory

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Summary

As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco Secure Email Gateway and Cisco Secure Email and Web Manager engineering team has conducted a comprehensive internal security review. This review resulted in software hardening releases that address multiple internally discovered vulnerabilities.

These vulnerabilities were found during internal testing. Two of them are known to be actively exploited.

For more information, see Cisco Secure Email Gateway SQL Injection Vulnerability and Cisco Secure Email Gateway Arbitrary File Write Vulnerability.

To assist customers in patching and streamline the disclosure process, Cisco has grouped these issues by their underlying vulnerability class — Common Weakness Enumeration (CWE) — and assigned a single Common Vulnerabilities and Exposures identifier (CVE ID) to each CWE grouping.

Cisco has released software updates that address these vulnerabilities. There are no workarounds that address these vulnerabilities.

Affected versions
  • Scope: These vulnerabilities affect Cisco Secure Email Gateway and Cisco Secure Email and Web Manager, regardless of device configuration.
  • Release 15.5 and earlier (first fixed: 15.5.5-014)
  • 16.0 — Migrate to a fixed release
  • Release 16.5 (first fixed: 16.5.0-780)
  • Release 15.5 and earlier (first fixed: 15.5.5-006)
  • Release 16.5 (first fixed: 16.5.0-429)

Official advisory · high-confidence parse· fetched 10 days ago·verify at source

Fixed versions
  • 15.5.5-014
  • 16.5.0-780
  • 15.5.5-006
  • 16.5.0-429

Official advisory · high-confidence parse· fetched 10 days ago·verify at source

Mitigation checklist

Recommended fix / mitigation
  • Upgrade to the first fixed release for your train per the Fixed Releases table in this advisory.
  • Release 15.5 and earlier: upgrade to 15.5.5-014.
  • Release 16.0: migrate to a fixed release.
  • Release 16.5: upgrade to 16.5.0-780.
  • Release 15.5 and earlier: upgrade to 15.5.5-006.
  • Release 16.0: migrate to a fixed release.
  • Release 16.5: upgrade to 16.5.0-429.
Workaround status
  • There are no workarounds that address these vulnerabilities.

Official advisory · high-confidence parse· fetched 10 days ago·verify at source

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