What is the CVSS score of CVE-2026-20127?

CVE-2026-20127 has a CVSS 3.1 base score of 10.0 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. EPSS exploitation probability: 2.6%.

Which versions of Sd Wan Vsmart Controller are affected by CVE-2026-20127?

A critical, actively exploited vulnerability in Cisco SD-WAN infrastructure allows unauthenticated attackers to gain administrative access without a patch currently available.

Is there a public PoC exploit available for CVE-2026-20127?

Yes, a public proof-of-concept exploit is available for CVE-2026-20127. Prioritise patching immediately. EPSS: 2.6%.

How to fix or mitigate CVE-2026-20127?

Within 24 hours: Identify all Cisco SD-WAN Controller and Manager instances in your environment and isolate them to restricted network segments with strict access controls. Within 7 days: Implement continuous monitoring for unauthorized access attempts and administrative account changes; engage Cisco TAC for interim mitigation guidance specific to your deployment. Within 30 days: Develop and execute a migration plan to patched versions as they become available; consider temporary SD-WAN failover to alternative solutions if risk tolerance is exceeded.

Sd Wan Vsmart Controller CVE-2026-20127

CRITICAL

Improper Authentication (CWE-287)

2026-02-25 psirt@cisco.com

Cisco Authentication Bypass Sd Wan Vsmart Controller Catalyst Sd Wan Manager

10.0

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

10.0 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

ENISA EUVD

HIGH

qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:55 vuln.today

Added to CISA KEV

Feb 26, 2026 - 16:20 cisa

CISA KEV

PoC Detected

Feb 26, 2026 - 16:20 vuln.today

Public exploit code

CVE Published

Feb 25, 2026 - 17:25 nvd

CRITICAL 10.0

DescriptionNVD

A vulnerability in the peering authentication in Cisco Catalyst SD-WAN Controller, formerly SD-WAN vSmart, and Cisco Catalyst SD-WAN Manager, formerly SD-WAN vManage, 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. 

Articles & Coverage 1

POC CVE-2026-20127: Cisco Catalyst SD-WAN Controller Authentication Bypass PoC Mar 09, 2026

AnalysisAI

Cisco Catalyst SD-WAN Controller and Manager contain a critical authentication bypass (CVE-2026-20127, CVSS 10.0) in the peering authentication mechanism that allows unauthenticated remote attackers to obtain full administrative privileges. The vulnerability exists because peering authentication does not properly validate credentials, enabling any attacker with network access to take over the SD-WAN management plane and control the entire WAN fabric.

Technical ContextAI

The peering authentication between SD-WAN controllers uses a flawed validation mechanism that can be bypassed by an unauthenticated attacker. SD-WAN controllers manage the entire overlay network — they distribute routing policies, security rules, and VPN configurations to all edge routers. Administrative access to vSmart/vManage means control over all traffic routing, segmentation, and security policies across every branch office and data center connected to the SD-WAN fabric.

RemediationAI

Apply Cisco security update immediately. Restrict control plane access to trusted management networks. Monitor for unauthorized peering sessions. Review SD-WAN configuration for unauthorized policy changes. Rotate all SD-WAN credentials and certificates after patching.