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On October 21, 2026, the Cisco Product Security Incident Response Team (PSIRT) published the following advisories. To remediate the vulnerabilities that were disclosed on October 21, 2026, Cisco strongly recommends that customers upgrade to the fixed software that is indicated in the advisories. For more information changes in Cisco PSIRT vulnerability disclosure, see Strengthening the Foundation: A Predictable, Customer-Focused Response to AI-Accelerated Vulnerability Discovery . Snort 3 Cisco Security Advisory CVE ID Security Impact Rating CVSS Base Score Multiple Cisco Products Snort 3 Security Hardening Release: October 2026 CVE-2026-20043 CVE-2026-20236 CVE-2026-20291 CVE-2026-20356 Critical 9.0 Open Source Snort 3 Control Channel Socket Arbitrary Command Execution Vulnerability CVE-2026-76524 High 7.8 Multiple Cisco Products Snort 3 Denial of Service Vulnerabilities CVE-2026-76489 CVE-2026-20019 CVE-2026-20179 CVE-2026-20197 Medium 5.8 Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerability CVE-2026-20221 Medium 5.8 Multiple Cisco Products Snort 3 SMTP MIME Denial of Service Vulnerability CVE-2026-20011 Medium 5.8 Multiple Cisco Products Snort 3 Visual Basic for Applications Buffer Overflow Denial of Service Vulnerability CVE-2026-20218 Medium 5.8 Multiple Cisco Products Snort 3 Denial of Service Vulnerability CVE-2026-76445 Medium 5.3 Cisco Expressway and Unified Communications Products Cisco Security Advisory CVE ID Security Impact Rating CVSS Base Score Cisco Expressway Series Remote Code Execution Vulnerability CVE-2026-76466 Critical 9.8 Cisco Expressway Series Security Hardening Release: October 2026 CVE-2026-76490 CVE-2026-76491 CVE-2026-76492 CVE-2026-76493 CVE-2026-76494 CVE-2026-76495 CVE-2026-76496 CVE-2026-76497 High 8.6 Cisco Expressway Series Information Disclosure Vulnerability CVE-2026-76435 Medium 5.3 Cisco Unified Communications Products Security Hardening Release: October 2026 CVE-2026-76476 CVE-2026-76473 CVE-2026-76475 CVE-2026-76477 CVE-2026-76478 CVE-2026-76479 CVE-2026-76481 CVE-2026-76474 Critical 9.8 Cisco Unified Communications Manager Improper Access Control Vulnerability CVE-2026-76487 Medium 5.3 Cisco IOS XR Software and Secure Client Cisco Security Advisory CVE ID Security Impact Rating CVSS Base Score Cisco IOS XR Software for ASR 9000 Series Routers IPv4 Unicast Packets Denial of Service Vulnerability CVE-2026-76505 High 7.5 Cisco Secure Client Secure Firewall Posture Module Privilege Escalation Vulnerability CVE-2026-76462 High 5.5

On October 21, 2026, the Cisco Product Security Incident Response Team (PSIRT) published the following advisories.

To remediate the vulnerabilities that were disclosed on October 21, 2026, Cisco strongly recommends that customers upgrade to the fixed software that is indicated in the advisories.

For more information changes in Cisco PSIRT vulnerability disclosure, see Strengthening the Foundation: A Predictable, Customer-Focused Response to AI-Accelerated Vulnerability Discovery .

Cisco Expressway and Unified Communications Products

Cisco IOS XR Software and Secure Client

Under the Cisco risk-based disclosure process, hardening releases and other security advisories are scheduled to publish on the first and third Wednesday of each month. To help customers prepare, we provide this seven-day advance notice of upcoming security vulnerability disclosures. However, this schedule is not a final commitment of releases. If updates are delayed or unforeseen changes arise, specific products may be removed and rescheduled. Products may also be added when releases are ready ahead of schedule. The latest status is available in the Revision History section of this advance notice.

Under the Cisco risk-based disclosure process, hardening releases and other security advisories are scheduled to publish on the first and third Wednesday of each month. To help customers prepare, we provide this seven-day advance notice of upcoming security vulnerability disclosures. However, this schedule is not a final commitment of releases. If updates are delayed or unforeseen changes arise, specific products may be removed and rescheduled. Products may also be added when releases are ready ahead of schedule. The latest status is available in the Revision History section of this advance notice.

Cisco Security Vulnerability Policy

To learn 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 .

To learn 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 .

Related to This Advisory

Version Description Section Status Date 1.0 Initial public release. - Interim 2026-OCT-14 Show Less

SOFTWARE DOWNLOADS AND TECHNICAL SUPPORT The Cisco Support and Downloads page on Cisco.com provides information 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 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.

SOFTWARE DOWNLOADS AND TECHNICAL SUPPORT

The Cisco Support and Downloads page on Cisco.com provides information 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 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.

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