CVE-2026-20127
Auth Bypass in Cisco Catalyst Sd-Wan Manager ≤ 20.9.8.2
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:HSummary
CVE-2026-20127 is a critical-severity Improper Authentication (CWE-287) vulnerability in Cisco Catalyst Sd-Wan Manager. Its CVSS base score is 10.0 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique External Remote Services (T1133); ranked in the top 0.2% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
The strongest mitigations our analysis identified map to IA-2 (Identification and Authentication (Organizational Users)) and IA-3 (Device Identification and Authentication) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-20127 is a critical vulnerability (CVSS 10.0, CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H) affecting the peering authentication mechanism in Cisco Catalyst SD-WAN Controller, formerly known as SD-WAN vSmart, and Cisco Catalyst SD-WAN Manager, formerly SD-WAN vManage. The issue stems from the peering authentication not functioning properly (CWE-287: Improper Authentication), enabling an unauthenticated remote attacker to bypass authentication controls and gain administrative privileges on affected systems.
An unauthenticated remote attacker can exploit this vulnerability by sending crafted requests to a vulnerable system. Successful exploitation allows the attacker to log in using an internal high-privileged non-root user account, providing access to NETCONF services. From there, the attacker can manipulate network configurations across the SD-WAN fabric, potentially disrupting operations or enabling further compromise.
The Cisco Security Advisory at https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sdwan-rpa-EHchtZk provides details on affected versions, exploitation status, and recommended mitigations or patches. This vulnerability is also listed in CISA's Known Exploited Vulnerabilities Catalog at https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-20127, indicating real-world exploitation and requiring urgent remediation by federal agencies.
Published on 2026-02-25, this flaw underscores risks in SD-WAN management platforms, with its perfect CVSS score highlighting the need for immediate patching in enterprise environments.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8675
Vulnerability Data
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…
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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.
- CWE(s)
- KEV Date Added
- 25 February 2026
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 8 hardening rules · 5 OS baselines
V6.4.4V6.5.4V6.5.5V6.5.7
Mitigating Controls (NIST 800-53 r5) AI
Mandates unique identification and authentication of organizational users before access, directly stopping improper authentication.
Requires unique identification and authentication of devices before establishing connections, preventing unauthenticated device claims.
Mandates unique identification and authentication of non-organizational users, directly addressing the weakness for external actors.
Manages authenticators with verification and secure distribution, reducing opportunities for improper authentication.
Enforces access only after approved authorizations, which presupposes correct authentication has occurred.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
PR.AA-03 directly enforces authentication mechanisms that eliminate most improper-authentication defects, yet CWE-287 spans additional vectors (missing checks, flawed protocols, session handling) that one control does not fully close.
PR.AA-04 directly enables verification of identity assertions (mostly preventing CWE-287 in that scope) yet leaves many other authentication failure modes unaddressed (only partial prevention overall).
PR.AA-01 supplies and governs credentials/tokens that authentication relies on, removing some weak-credential cases, yet leaves verification logic, missing checks, and protocol flaws untouched.
PR.AA-02 ensures valid enrollment and unique credential binding, which reduces some improper-auth risks at issuance time but leaves runtime claim verification untouched, so each direction only partially addresses the other.
PR.PS-01 can enforce auth-related settings via hardened baselines and default reviews, blocking some config-based instances of CWE-287, yet leaves code-level auth flaws untouched so neither direction reaches mostly.
Patching/maintenance can remediate some known auth vulnerabilities after deployment (partial forward) but does not address the design or implementation of authentication logic itself (none reverse).
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Requiring authentication methods whose strength matches the sensitivity of the data and mandating multi-factor authentication directly blocks attempts to access resources without proving identity.
Verifying user identity before issuing replacement credentials and forcing changes after compromise reduces the likelihood that authentication bypass can be achieved through stolen or weak credentials.
Mandating segregated approval and oversight for non-human identities reduces the chance that weak or orphaned credentials can be exploited for unauthorized authentication.
Requiring authentication mechanisms and technical parameters for secure connections ensures that network services verify user identity before granting access, preventing exploitation of missing or weak authentication.
Security requirements specified early and verified through testing drive the consistent implementation of authentication mechanisms, decreasing the likelihood that authentication steps are omitted or incorrectly applied.
Defining the required level of trust in entity identity and the authentication mechanisms to achieve it ensures that authentication is explicitly addressed rather than omitted.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (1 rule)
- V-248827 OL 8 must not have the rsh-server package installed. prevents CWE-287
RHEL 7 (3 rules)
- V-204425 The Red Hat Enterprise Linux operating system must be configured so that the SSH daemon does not allow authentication using an empty password. prevents CWE-287
- V-204442 The Red Hat Enterprise Linux operating system must not have the rsh-server package installed. prevents CWE-287
- V-204424 The Red Hat Enterprise Linux operating system must not allow accounts configured with blank or null passwords. prevents CWE-287
RHEL 8 (1 rule)
- V-230492 RHEL 8 must not have the rsh-server package installed. prevents CWE-287
Ubuntu 22.04 (1 rule)
- V-260470 Ubuntu 22.04 LTS, when booted, must require authentication upon booting into single-user and maintenance modes. prevents CWE-287
Ubuntu 24.04 (2 rules)
- V-270675 Ubuntu 24.04 LTS when booted must require authentication upon booting into single-user and maintenance modes. prevents CWE-287
- V-270714 Ubuntu 24.04 LTS must not allow accounts configured in Pluggable Authentication Modules (PAM) with blank or null passwords. prevents CWE-287