Dark Reading27 Feb 2026
Cisco SD-WAN Zero-Day Under Exploitation for 3 Years
The maximum-severity vulnerability CVE-2026-20127 was exploited by an unknown but sophisticated threat actor who left very little evidence behind.
Actively exploited vulnerability
CVE-2026-20127: Cisco Catalyst SD-WAN Controller and Manager Authentication Bypass Vulnerability
Cisco Catalyst SD-WAN Controller, formerly SD-WAN vSmart, and Cisco Catalyst SD-WAN Manager, formerly SD-WAN vManage, contain an authentication bypass vulnerability could allow an unauthenticated, remote attacker to bypass authentication and obtain administrative privileges on an affected system. This vulnerability exists because the peering authentication mechanism in an affected system is not working properly. An attacker could exploit this vulnerability by sending crafted requests to an affected system. A successful exploit could allow the attacker to log in to an affected Cisco Catalyst SD-WAN Controller as an internal, high-privileged, non-root user account. Using this account, the attacker could access NETCONF, which would then allow the attacker to manipulate network configuration for the SD-WAN fabric.
CISA KEV source
25 Feb 2026 added
27 Feb 2026 remediation due
Affected product
Cisco · Catalyst SD-WAN Controller and Manager
Known ransomware use: Unknown
Required action
Follow the source advisory and validate exposure in your environment.
Please adhere to CISA’s guidelines to assess exposure and mitigate risks associated with Cisco SD-WAN devices as outlines in CISA’s Emergency Directive 26-03 (URL listed below in Notes) and CISA’s “Hunt & Hardening Guidance for Cisco SD-WAN Devices (URL listed below in Notes). Adhere to the applicable BOD 22-01 guidance for cloud services or discontinue use of the product if mitigations are not available.
Related Yasna coverage
Recent reporting that mentions CVE-2026-20127.
The Hacker News26 Feb 2026
Cisco SD-WAN Zero-Day CVE-2026-20127 Exploited Since 2023 for Admin Access
A newly disclosed maximum-severity security flaw in Cisco Catalyst SD-WAN Controller (formerly vSmart) and Catalyst SD-WAN Manager (formerly vManage) has come under active exploitation in the wild as part of malicious activity that dates back to 2023
Bleeping Computer26 Feb 2026
Critical Cisco SD-WAN bug exploited in zero-day attacks since 2023
Cisco is warning that a critical authentication bypass vulnerability in Cisco Catalyst SD-WAN, tracked as CVE-2026-20127, was actively exploited in zero-day attacks that allowed remote attackers to compromise controllers and add malicious rogue peers to targeted networks. [...]