Cisco Security Advisory
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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
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A vulnerability in the API session-based authentication management of Cisco Catalyst SD-WAN Manager could allow an unauthenticated, remote attacker to access an affected system with privileges of the admin user.
This vulnerability is due to improper handling of URI encoding in an HTTP request, which allows the request to bypass an authentication rule that is intended to restrict access to a specific API endpoint. An attacker could exploit this vulnerability by sending a crafted HTTP request to the API of the affected system. A successful exploit could allow the attacker to bypass authentication and gain access to the API as the admin user.
Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.
This advisory is available at the following link:
https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sdwan-webauth-xr8beuuU
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Vulnerable Products
This vulnerability affects Cisco Catalyst SD-WAN Manager, regardless of system 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 this vulnerability.
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Cisco Catalyst SD-WAN Manager systems that are exposed to the internet and that have ports exposed to the internet are at risk of exposure to compromise. In some instances, these indicators of compromise (IOCs) may occur during standard operations. Therefore, they must be assessed against normal network posture to identify and avoid false positives.
Important: These IOC examples show the use of %6a as the URI encoded character j in the request. This is only an example, and the vulnerability will allow any one character that is encoded in the request to be used to exploit this.
Customers are encouraged to audit the serviceproxy-access.log file, located at /var/log/nms/containers/service-proxy/serviceproxy-access.log, for entries that are related to j_security_check from unknown or unauthorized IP addresses, as shown in the following example:
[2026-09-29T23:11:13.948-05:00] "POST /%6a_security_check HTTP/1.1" 200 - 48 0 4 - "10.10.10.47,192.168.1.174" "Mozilla/5.0" "92980fc6-bb3c-4b67-8a6d-af5ceb236d4c" "vmanage-9999.example.com" "127.0.0.1:8080"
Customers are encouraged to audit the vmanage-server.log file, located at /var/log/nms/vmanage-server.log, for entries that are related to j_security_check from unknown or unauthorized IP addresses, specifically being called for users that include names starting with viptela-reserved-, as shown in the following example:
29-Sep-2026 23:11:13,952 CDT [] [vManage-new] [UserUtils] (default task-127462) |default| Request Stored in Map is (/%6a_security_check) for user (viptela-reserved-..)
For help determining if Cisco Catalyst SD-WAN Manager has been compromised, customers may open a case with the Cisco Technical Assistance Center (TAC). Cisco TAC cases should be opened as a Severity 3 with the CVE-ID CVE-2026-76504 in the title. Before opening a new TAC case, customers are encouraged to use the request admin-tech command from the Cisco Catalyst SD-WAN Manager (vManage) in the SD-WAN deployment so that the admin-tech file can be provided to the Cisco TAC for review.
The viptela-reserved system service accounts are documented in the Authentication, Authorization, and Accounting section of the Cisco Catalyst SD-WAN Systems and Interfaces Configuration Guide.
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There are no workarounds that address this vulnerability. However, as a mitigation for On-Prem deployment customer environments, they should restrict access from unsecured networks, such as the internet, to the system. If access to the system is required from the internet, restrict system access to only known, trusted hosts on ports and protocols that are included in the user guides. Protect Cisco Catalyst SD-WAN Control Components behind a filtering device such as a firewall, and filter traffic to and from the system while allowing only known, trusted hosts to send traffic to the system. For more information, see the Cisco Catalyst SD-WAN Hardening Guide.
For Cisco Catalyst SD-WAN Cloud Hosted environments, this mitigation is already deployed.
While this mitigation has been deployed and was proven successful in a test environment, customers should determine the applicability and effectiveness in their own environment and under their own use conditions. Customers should be aware that any workaround or mitigation that is implemented may negatively impact the functionality or performance of their network based on intrinsic customer deployment scenarios and limitations. Customers should not deploy any workarounds or mitigations before first evaluating the applicability to their own environment and any impact to such environment.
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Cisco considers any workarounds and mitigations (if applicable) to be temporary solutions until an upgrade to a fixed software release is available. To remediate this vulnerability 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 table(s), the left column lists Cisco software releases. The right column indicates whether a release is affected by the vulnerability that is described in this advisory and the first release that includes the fix for this vulnerability. Customers are advised to upgrade to an appropriate fixed software release as indicated in this section.
Cisco Catalyst SD-WAN Software Release First Fixed Release Earlier than 20.9 Migrate to a fixed release. 20.9 20.9.10.1 20.12 20.12.8.2 20.15 20.15.6.1 20.18 20.18.4.1 26.1 26.1.2.1 26.2 26.2.1 Cisco has also addressed this vulnerability in Cisco SD-WAN Cloud (Cisco Managed) Release 20.15.605, which is cloud based. No user action is required. Customers can determine the current remediation status or software version by using the Help function in the service GUI.
Customers who need additional information are advised to contact the Cisco TAC or their contracted maintenance providers.
The Cisco Product Security Incident Response Team (PSIRT) validates only the affected and fixed release information that is documented in this advisory.
Additional Information
- To check component and software release compatibility, see the Catalyst SD-WAN Control Component Compatibility Matrix.
- For help planning an upgrade, see the Cisco Catalyst SD-WAN Upgrade Matrix.
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Cisco recommends upgrading the affected systems to a fixed software release.
General Recommendations for Hardening
- Prevent access from unsecured networks, such as the internet, to the system. If internet access to the system is required, restrict system access to only known, trusted hosts on ports and protocols that are included in the user guides.
- Protect Cisco Catalyst SD-WAN Control Components behind a filtering device such as a firewall, and filter traffic to and from the systems while allowing only known, trusted hosts to send traffic to the systems. Using a two-layer firewall can provide flexibility in network planning so that end users do not connect directly to the outer DMZ. See the Deployment sections of the User Guides for Cisco Catalyst SD-WAN software.
- Regularly monitor web log traffic for any unexpected traffic to and from systems. Logging should be sent to an external server, if possible, and kept for a long enough duration so that post-event investigations can be performed with sufficient log data.
- Upgrade the system to the latest version of Cisco Catalyst SD-WAN Software.
- Change the default administrator password to a more secure variant. Restrict access to the administrator account by creating user accounts based on necessary access requirements. In addition, create operator accounts for all administrators.
- When using SSL/TLS, obtain an SSL certificate from a certificate authority (CA).
For more information, review the Cisco Catalyst SD-WAN Hardening Guide.
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In September 2026, the Cisco PSIRT became aware of active exploitation of this vulnerability. Cisco strongly recommends that customers upgrade to a fixed software release to remediate this vulnerability.
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This vulnerability was found during the resolution of a Cisco Technical Assistance Center (TAC) support case.
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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.
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Show LessVersion Description Section Status Date 1.0 Initial public release. — Final 2026-SEP-30
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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.