Known exploited vulnerability · CISA KEV

CVE-2026-76504: Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability

Cisco Catalyst SD-WAN Manager contains a hex encoding vulnerability that could allow an unauthenticated, remote attacker to access an affected system with privileges of the admin user due to improper handling of URI encoding in an HTTP request.

CVE-2026-76504

Exploited in the wild. Fix this first.

CISA added it to the Known Exploited Vulnerabilities catalog on 2026-09-30: attackers are using it right now.

CISA KEV: Listed; Added 2026-09-30 · federal fix-by 2026-10-03
EPSS (30 days): 39%; Higher than 99% of CVEs · 2026-11-01
CVSS v3.1: 9.8 Critical; CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

What CISA says

Cisco Catalyst SD-WAN Manager Hex Encoding Vulnerability

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

NVD description · published 2026-09-30

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.

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How to check if you are exposed to CVE-2026-76504

Find every Cisco Catalyst SD-WAN Manager system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
Compare each version with the fixed versions in the vendor advisory below. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2026-76504.

US federal agencies had to fix this by 2026-10-03. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.

Affected versions

Versions the National Vulnerability Database lists as vulnerable to CVE-2026-76504. Check the vendor advisory for the exact fixed builds before you sign anything off.

Product	Vulnerable versions
Cisco Catalyst Sd-Wan Manager	before 20.9.10.1; from 20.12 before 20.12.8.2; from 20.15 before 20.15.6.1; from 20.18 before 20.18.4.1; from 26.1 before 26.1.2.1; 26.2

Timeline

2026-09-30 · Published in the National Vulnerability Database
2026-09-30 · Added to CISA's Known Exploited Vulnerabilities catalog, the same day it was published
2026-10-03 · Fix-by date for US federal agencies, passed 29 days ago

Vendor advisories and fixes

https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sdwan-webauth-xr8beuuU

Weakness type

CWE-177

More exploited Cisco vulnerabilities

CISA lists 102 exploited Cisco vulnerabilities. The closest matches:

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Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.