Overview
Cisco Catalyst SD-WAN Controller and Manager contain a critical authentication bypass vulnerability in the peering authentication mechanism. This flaw allows unauthenticated remote attackers to obtain administrative privileges by sending specially crafted requests to the affected systems. The vulnerability was disclosed on February 25, 2026. CISA has identified CVE-2026-20127 as being exploited but is not currently known to be used in ransomware campaigns.
Technical details
The vulnerability exists in the peering authentication mechanism of Cisco Catalyst SD-WAN Controller and Manager. The authentication logic fails to properly validate the credentials and authenticity of peer connections, allowing unauthenticated remote attackers to bypass authentication controls. By crafting malicious requests that exploit this authentication bypass, an attacker can escalate privileges to obtain full administrative access to the affected SD-WAN infrastructure.
The vulnerability is classified as CWE-287 (Improper Authentication) , CWE-269 (Improper Access Control) andCWE-284 (Improper Access Control) .
The vulnerability has received a CVSS v3.1 base score of 9.8 (CRITICAL) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H, indicating its critical nature.
Impact
Successful exploitation of this vulnerability allows unauthenticated remote attackers to gain full administrative privileges on the Cisco Catalyst SD-WAN Controller or Manager. With administrative access, attackers can: - View, modify, or delete sensitive SD-WAN configurations - Access and exfiltrate confidential network traffic and business data - Modify SD-WAN policies to redirect or intercept traffic - Disrupt SD-WAN operations and services - Pivot to other network infrastructure connected through the SD-WAN - Deploy malicious configurations affecting multiple branch locations - Establish persistent backdoors for long-term unauthorized access This vulnerability is particularly critical as SD-WAN controllers manage critical network infrastructure and security policies across organizations. An attacker gaining administrative access could compromise the entire SD-WAN fabric and connected enterprise networks.
Mitigation and workarounds
1. Download the latest patched version from Cisco's support portal 2. Back up the current configuration 3. Follow Cisco's documented upgrade procedures for your specific deployment 4. Test the update in a non-production environment first 5. Apply the patch during a maintenance window 6. Verify system functionality and peering authentication after upgrade The following versions include the necessary fixes: Cisco Catalyst SD-WAN Controller 20.13.3 and later, Cisco Catalyst SD-WAN Manager 20.13.3 and later.
As temporary workarounds: implement network-level access controls to restrict administrative interfaces to trusted ip addresses and networks only. use firewall rules to limit inbound connections to the catalyst sd-wan controller/manager management ports (typically 443/https) to authorized administrative networks.; disable or restrict the peering authentication feature if not required for your sd-wan deployment, though this may impact sd-wan functionality depending on your network topology., and implement continuous monitoring and alerting on authentication failures and privilege escalation attempts. log all administrative access and review logs regularly for suspicious activity..
CISA's recommendation: 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.
Additional resources
Source: This report was generated using AI
