Critical Cisco Catalyst SD-WAN Manager API authentication bypass exploited in the wild (CVE-2026-76504)

A flaw in the peering authentication mechanism of Cisco Catalyst SD-WAN Controller (formerly vSmart), Manager (formerly vManage), and Validator (formerly vBond) allows an unauthenticated, remote attacker to bypass authentication by sending crafted requests to an affected system. A successful exploit grants the attacker access as an internal, high-privileged, non-root user on the SD-WAN Controller, from which they can reach NETCONF and manipulate the network configuration of the entire SD-WAN fabric. Any organization operating these Cisco SD-WAN control-plane components is affected, and the critical CVSS 10.0 score reflects full network scope with no privileges or user interaction required. The flaw is confirmed exploited in the wild: CISA added it to the KEV on 2026-02-25, Cisco has confirmed active exploitation (including a compromise of a communications service provider), and Five Eyes allies have issued an active-exploitation warning, with EPSS at 88.2% (100th percentile).

Do: Upgrade affected Catalyst SD-WAN Controller, Manager, and Validator components per Cisco's PSIRT advisory (fixed versions are not specified in this data), and prioritize patching given confirmed in-the-wild exploitation. Follow CISA Emergency Directive 26-03 and the CISA Hunt & Hardening Guidance for Cisco SD-WAN Devices: hunt for compromise indicators such as unexpected high-privileged non-root logins and unauthorized NETCONF configuration changes, and restrict internet exposure of SD-WAN management interfaces. Where mitigations are unavailable, adhere to applicable BOD 22-01 cloud guidance or discontinue use of the product.

CVE-2026-20182 is a critical authentication flaw (CWE-287) in the control-connection peering authentication of Cisco Catalyst SD-WAN Controller (formerly vSmart), Manager (formerly vManage), and Validator (formerly vBond). Because the peering authentication mechanism does not work properly, an unauthenticated, remote attacker can send crafted requests during the control-connection handshake and log in to the controller as an internal, high-privileged, non-root user without valid credentials. With this access, the attacker can reach NETCONF and manipulate network configuration across the entire SD-WAN fabric. Any organization running these Catalyst SD-WAN control components is affected, and the flaw carries a CVSS 3.1 score of 10.0 and a 91.5% EPSS score. CISA added it to the Known Exploited Vulnerabilities catalog on 2026-05-14, confirming exploitation in the wild, amid a series of exploited Cisco SD-WAN zero-days including a compromise at a communications service provider.

Do: Upgrade affected Catalyst SD-WAN Controller, Manager, and Validator components to the fixed releases identified in Cisco's May 2026 advisory (version numbers are not provided in this data). Use the advisory's 'show control connections' guidance to inspect control-connection handshaking for anomalies and audit for unauthorized high-privileged non-root accounts and unexpected NETCONF sessions. Operators — especially federal agencies — should follow CISA Emergency Directive 26-03 and CISA's Hunt & Hardening Guidance for Cisco SD-WAN Devices, including restricting internet exposure of SD-WAN management interfaces until patched.

Cisco Catalyst SD-WAN Manager has a critical flaw in how it manages API session authentication. Improper handling of URI encoding in an HTTP request can bypass an authentication rule that is supposed to restrict a specific API endpoint. An unauthenticated remote attacker can send a crafted HTTP request and gain access to the API with admin privileges, affecting confidentiality, integrity, and availability (CVSS 9.8). Organizations that run Catalyst SD-WAN Manager are affected; the provided data does not list vulnerable or fixed version ranges. No public proof-of-concept is known and the issue is not in CISA's Known Exploited Vulnerabilities catalog.

Do: Install Cisco's fixed release for Catalyst SD-WAN Manager as soon as it is available for your deployment; the supplied data does not name vulnerable or fixed versions. Until patched, keep the Manager API off the internet and limit it to trusted management networks, and review API logs for unexpected unauthenticated requests that reach admin-only endpoints.