CVE-2026-20127

Cisco Catalyst SD-WAN Controller Authentication Bypass Vulnerability

Exploited in the wild. In CISA KEV since 2026‑02‑25. A vendor fix is available.

CVSS 3.110.0Critical EPSS percentile99th88% chance in 30 days CISA KEVListedsince 2026-02-25, due 2026-02-27
Public exploit: 0 sources FixVendor fixNo build named by the sources

Published 2026-02-25Updated 2026-06-17Sources: CVE.org, NVD, BDU

NVD CVE.org

What to do

The vendor has published a fix. Version details are below where the sources state them.

Steps

Written by AI from the record

Check whether you use Cisco catalyst sd-wan manager, sd-wan vbond orchestrator, sd-wan vsmart controller, cisco catalyst sd-wan controller, or cisco catalyst sd-wan manager, and whether they could be reachable from the network (directly or via SD-WAN peering paths).
Confirm your current running software version(s) on each affected device.
Upgrade all affected SD-WAN components to the fixed release: 20.9.8.2.
If you cannot upgrade immediately, restrict network access so the devices are not reachable from untrusted networks and follow Cisco/CISA hardening guidance until upgrades are completed.
After upgrading, monitor for signs of unauthorized configuration changes and validate that SD-WAN controller/peering status and configuration match your expected state.

Vendor advisory Usually a quick update

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

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

In plain language

Written by AI from the record

CVE-2026-20127 lets an attacker bypass login to Cisco Catalyst SD-WAN controllers and make high-privilege changes to your network; if you run these products, you should treat this as an immediate, serious risk.

CVE-2026-20127 is an authentication-bypass flaw (CWE-287) in Cisco Catalyst SD-WAN peering authentication, where an unauthenticated remote attacker can send crafted requests to bypass authentication, obtain an administrative session, and then use NETCONF to manipulate SD-WAN network configuration; it is confirmed in CISA KEV and has been reported exploited in real attacks.

If you're affected

Full SD-WAN configuration takeover
Service disruption and outage risk
Unauthorized network traffic changes
Loss of administrative control

What is it

This is a serious weakness in the login/connection process between Cisco SD-WAN network controllers. An attacker may be able to pretend they are trusted, get administrative access, and then change how your SD-WAN routes and network settings work—similar to walking past the front desk and opening the server-room control panel.

Because it can lead to administrative control and configuration changes, it can disrupt service and let an attacker steer network traffic.

Who is affected

This matters if your business uses Cisco Catalyst SD-WAN controller components—specifically catalyst sd-wan manager, sd-wan vbond orchestrator, sd-wan vsmart controller, cisco catalyst sd-wan controller, or cisco catalyst sd-wan manager.

This is an internet/network-reachable authentication bypass with no login or user action needed, so the risk is highest when the device is reachable from an attacker’s network path (including peering-related communication paths) and when peering authentication is not working properly.

How urgent is it

This is RED because attackers have been reported exploiting it in the real world, and it is also listed in CISA’s KEV (confirmed exploitation). The vulnerability allows bypassing authentication and obtaining administrative capability to change SD-WAN configuration.

Act immediately by checking exposure and upgrading to the fixed release across all affected SD-WAN components.

What to do — in detail

Confirm which devices we run
- Inventory all SD-WAN controller components: catalyst sd-wan manager, sd-wan vbond orchestrator, sd-wan vsmart controller, cisco catalyst sd-wan controller, and cisco catalyst sd-wan manager.
- For each system, record the software version currently installed.
Determine exposure (reachability)
- Check network/security appliance rules and routing to see whether these devices are reachable from untrusted networks.
- Pay special attention to any SD-WAN peering/communication paths and any interfaces/security policies that could allow inbound crafted requests.
- If “reachable in default config” is unknown in your environment, treat it as potentially reachable until verified.
Remediate (upgrade to the fixed version)
- Upgrade all affected components to 20.9.8.2.
- Do this as a coordinated change so all SD-WAN controller roles align on the fixed release.
- Note: the CISA KEV due date for remediation is 2026-02-27.
Temporary containment if upgrade is delayed
- Block or restrict inbound access to these SD-WAN controller endpoints from untrusted networks.
- Ensure peering-related communication is limited to only the expected partner IPs/networks and required protocols.
- Apply Cisco/CISA “Hunt & Hardening Guidance for Cisco SD-WAN Devices” while you complete the upgrade.
Validate after patching
- Re-verify the running version is 20.9.8.2 on each affected device.
- Review logs for evidence of unauthorized access attempts and, critically, any NETCONF/configuration changes that were not initiated by your administrators.
- Compare current SD-WAN configuration and controller/peering status to your known-good baseline.
Keep monitoring
- Continue monitoring for suspicious administrative actions and configuration drift until you are confident there is no ongoing compromise.

Technical context

Severity is critical (CVSS 10 in the provided data) because the issue enables full administrative impact without needing authentication or user interaction.

Mechanism: a weakness in Cisco Catalyst SD-WAN peering authentication (CWE-287, authentication bypass). An attacker can send crafted network requests to bypass authentication, log in as an internal high-privileged (non-root) user, and then use NETCONF to manipulate SD-WAN fabric configuration.

Exploitation status: CISA KEV listing is confirmed (added 2026-02-25) with a remediation due date of 2026-02-27, and real-world exploitation has been reported. Public exploitation exists, and press reports indicate possible prior targeting of SD-WAN Manager systems during zero-day activity.

Fix: the vendor fixed affected components in version 20.9.8.2 for catalyst sd-wan manager, sd-wan vbond orchestrator, and sd-wan vsmart controller. KEV/real-world exploitation take precedence over the EPSS prediction; therefore, exploitation likelihood is treated as established rather than probabilistic.

This is a general assessment based on public vulnerability data. It does not account for your specific infrastructure — when in doubt, consult a security specialist.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS99th

Public exploit

CISA KEV

Listed as exploited in the wild since 2026-02-25.

US federal agencies must remediate by 2026-02-27.

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.

Public exploits

0 sources with a proof of concept or module.

Exploit links, PoCs and Metasploit modules after sign-in

EPSS

88% chance of exploitation activity in the next 30 days, which ranks it in the 99th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

16 events over 124 days, from the signal feeds we watch.

2026-06-29EPSS band changemoderate → high
2026-06-28EPSS band changemoderate → high
2026-06-27EPSS band changemoderate → high
2026-06-25OpenVAS check added
2026-06-23EPSS band changemoderate → high
2026-06-22EPSS band changehigh → moderate

Affected products

Cisco Systems Inc.commercial · USaka cisco, cisco systems

And 1 more affected product. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 10.0 by NVD.

How it is reached

Attack Vector NetworkExploitable remotely over the network without any special conditions
Attack Complexity LowNo special conditions — the attack can be reliably reproduced
Privileges Required NoneNo authentication required — anyone can exploit this
User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

Scope ChangedThe exploit can affect other components (e.g. sandbox escape, host compromise from VM)

Impact if exploited

Confidentiality HighTotal information disclosure — all data in the component is compromised
Integrity HighTotal loss of integrity — attacker can modify any data in the component
Availability HighTotal denial of service — the component is completely unavailable