What is CVE-2026-76504?
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.
Timeline
- 2026-09-30Published to the U.S. National Vulnerability Database (NVD)
- 2026-09-30Added to the CISA Known Exploited Vulnerabilities (KEV) catalog
- 2026-10-01First covered in a defend.network daily briefing
- 2026-10-03CISA federal remediation deadline (BOD 22-01)
CISA Known Exploited Vulnerability
Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability
Affected product
Cisco Catalyst SD-WAN Manager
Remediation Steps
- Apply fixed release from Cisco, as no workaround is available
- Isolate Catalyst SD-WAN Manager instances from untrusted networks
- Monitor API access logs for unauthorized admin-level activity
- Verify all recent API access and configuration changes for signs of compromise
References
- https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sdwan-webauth-xr8beuuU
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-76504
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog
- https://nvd.nist.gov/vuln/detail/CVE-2026-76504
Referenced in our briefings & reports
- Vulnerability Priority Report – Week 4 of September 2026 (September 28 – October 4)
- Cisco SD-WAN, Zimbra, Zammad under attack; active exploitation confirmed (2026-10-01)
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