Cisco Security Advisory
Cisco Secure Email Gateway and Secure Email and Web Manager Security Hardening Release: September 2026
Click Icon to Copy Verbose Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:X/RL:X/RC:X
-
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. One of them is known to be actively exploited. For more information, see Cisco Secure Email Gateway SQL Injection 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.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-esa-dfCrfXkm
-
Vulnerable Products
These vulnerabilities affect Cisco Secure Email Gateway and Cisco Secure Email and Web Manager, regardless of device configuration.
For information about which Cisco software releases are vulnerable, see the Fixed Software section of this advisory.
Products Confirmed Not Vulnerable
Only products listed in the Vulnerable Products section of this advisory are known to be affected by these vulnerabilities.
Cisco has confirmed that these vulnerabilities do not affect Cisco Secure Web Appliance.
-
The following table outlines the vulnerability classes that are addressed in these software hardening releases. The CVSS score that is assigned to each CVE ID represents the maximum potential severity of the single most impactful underlying vulnerability within that specific CWE category.
CVE ID Highest CVSS Score Vulnerability Class (Highest-Level CWE) Description CVE-2026-76440 9.8 CWE-23 Path traversal (covers improper limitation of a pathname to a restricted directory and improper link resolution before file access) CVE-2026-76441 9.8 CWE-284 Improper access control (covers authorization, authentication, privileges, and bypasses) CVE-2026-20353 9.8 CWE-664 Improper control of a resource through its lifetime (covers uncontrolled resource consumption, algorithmic complexity, recursion/iteration, deserialization, and improper resource initialization) CVE-2026-76443 9.8 CWE-707 Improper neutralization1 (covers command, SQL, and code/eval injection, and cross-site scripting) CVE-2026-76442 7.5 CWE-1284 Improper validation of specified quantity in input (covers unbounded numeric fields that drive excessive resource consumption) 1. One vulnerability that belongs to this vulnerability class is known to be actively exploited. For more information, see Cisco Secure Email Gateway SQL Injection Vulnerability.
-
There are no workarounds that address these vulnerabilities.
-
To remediate these vulnerabilities and avoid future exposure as described in this advisory, Cisco strongly recommends that customers upgrade to the fixed software indicated in this advisory.
Fixed Releases
In the following tables, the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerabilities that are described in this advisory and the first release that includes the fix for these vulnerabilities. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.
Cisco Secure Email Gateway Release First Fixed Release 15.5 and earlier 15.5.5-014 16.0 Migrate to a fixed release. 16.5 16.5.0-780
Cisco Secure Email and Web Manager Release First Fixed Release 15.5 and earlier 15.5.5-006 16.0 Migrate to a fixed release. 16.5 16.5.0-429 The software can be upgraded over the network by using the System Upgrade options in the web-based management interface of the appliance.
To upgrade a device by using the web-based management interface, do the following:
- Choose System Administration > System Upgrade.
- Click Upgrade Options.
- Click Download and Install.
- Choose a release to upgrade to.
- In the Upgrade Preparation area, choose the appropriate options.
- Click Proceed to begin the upgrade. A progress bar displays the status of the upgrade.
After the upgrade is complete, the device reboots.
To upgrade a device by using the CLI, do the following:
- Run upgrade.
- Enter DOWNLOADINSTALL.
- Choose a release to upgrade to.
- Choose the appropriate options throughout the upgrade process.
After the upgrade is complete, the device reboots.
Cisco Secure Email Cloud includes Cisco Secure Email Gateway and Cisco Secure Email and Web Manager devices as part of the service solution. Cisco provides regular maintenance of the products included in this solution. Customers can also request a software upgrade by contacting Cisco Secure Email Cloud support.
The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.
-
Except as otherwise noted previously, the Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerabilities that are described in this advisory.
-
These vulnerabilities were found during internal security testing using existing testing processes as well as frontier AI models.
-
To learn about Cisco security vulnerability disclosure policies and publications, see the Security Vulnerability Policy. This document also contains instructions for obtaining fixed software and receiving security vulnerability information from Cisco.
For additional information on Cisco's vulnerability management, disclosure cadence, and software patching strategy, see Cisco's Transition to a Risk-Based Vulnerability Disclosure Model.
-
Show LessVersion Description Section Status Date 1.0 Initial public release. - Final 2026-SEP-14
-
SOFTWARE DOWNLOADS AND TECHNICAL SUPPORT
The Cisco Support and Downloads page on Cisco.com provides information about licensing and downloads. This page can also display customer device support coverage for customers who use the My Devices tool. Please note that customers may download only software that was procured from Cisco directly or through a Cisco authorized reseller or partner and for which the license is still valid.
Customers who purchase directly from Cisco but do not hold a Cisco service contract and customers who make purchases through third-party vendors but are unsuccessful in obtaining fixed software through their point of sale should obtain upgrades by contacting the Cisco Technical Assistance Center (TAC). Customers should have the product serial number available and be prepared to provide the URL of this advisory as evidence of entitlement to a free upgrade.
When considering software upgrades, customers are advised to regularly consult the advisories for the relevant Cisco products to determine exposure and a complete upgrade solution. In all cases, customers should ensure that the devices to be upgraded contain sufficient memory and confirm that current hardware and software configurations will continue to be supported properly by the new release. If the information is not clear, customers are advised to contact the Cisco Technical Assistance Center (TAC) or their contracted maintenance providers.
LEGAL DISCLAIMER DETAILS
CISCO DOES NOT MAKE ANY EXPRESS OR IMPLIED GUARANTEES OR WARRANTIES OF ANY KIND, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. WITHOUT LIMITING THE GENERALITY OF THE FOREGOING, CISCO DOES NOT GUARANTEE THE ACCURACY OR COMPLETENESS OF THIS INFORMATION. THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
Copies or summaries of the information contained in this Security Advisory may lack important information or contain factual errors. Customers are advised to visit the Cisco Security Advisories page for the most recent version of this Security Advisory. The Cisco Product Security Incident Response Team (PSIRT) assesses only the affected and fixed release information that is documented in this advisory. See the Cisco Security Vulnerability Policy for more information.