Cisco has patched yet another Catalyst SD-WAN Controller authentication bypass vulnerability (CVE-2026-20182) that has been exploited as a zero-day by “a highly sophisticated cyber threat actor”.

About CVE-2026-20182

CVE-2026-20182 – affecting both Cisco Catalyst SD-WAN Controller (the “brain” of the Cisco Catalyst SD-WAN solution) and Cisco Catalyst SD-WAN Manager (the management plane for the entire SD-WAN fabric) – stems from a flawed peering authentication mechanism. It affects both on-prem and cloud deployments.

CVE-2026-20182 was reported to Cisco by Rapid7 researchers Jonah Burgess and Stephen Fewer, who discovered it while researching CVE-2026-20127, another auth bypass flaw (CVE-2026-20127) that was spotted being exploited earlier this year.

Both vulnerabilities can be exploited by sending crafted requests to the affected system, and may allow attackers to log in to an affected Cisco Catalyst SD-WAN Controller as an internal, high-privileged, non-root user account.

“This new authentication bypass vulnerability affects the ‘vdaemon’ service over DTLS (UDP port 12346), which is the same service that was vulnerable to CVE-2026-20127,” Rapid7 researchers explained.

The issue is located in a similar part of the “vdaemon” networking stack, but the impact is the same.

“A remote unauthenticated attacker can leverage CVE-2026-20182 to become an authenticated peer of the target appliance, and perform privileged operations, such as injecting an attacker controlled public key into the vmanage-admin user account’s authorized SSH keys file,” Fewer and Burgess noted.

“Once this has been performed, a remote unauthenticated attacker can login to the NETCONF service (SSH over TCP port 830) as the vmanage-admin user, and begin to issue arbitrary NETCONF commands [to reconfigure the SD-WAN fabric].”

Cisco’s threat analysts tied the exploitation of both vulnerabilities to a group they dubbed “UAT-8616”.

In previously detected attacks, the group escalated their privileges to root by downgrading the software versions and exploiting an older privilege escalation vulnerability (CVE-2022-20775). After that, they restored back the original software version.

Cisco did not speculate on the provenance or nature of UAT-8616, though it said that the infrastructure used by the group to carry out exploitation and post-compromise activities overlaps with the Operational Relay Box (ORB) networks its researchers are monitoring.

Google Mandiant researchers previously stated that China-nexus threat actors use ORB networks when conducting espionage operations.

What to do?

Cisco says that CVE-2026-20182 exploitation seems to be limited, so far, but did not specify which organizations are likely to have been targeted.

The company advises customers to upgrade to a fixed software release of the software and to review SD-WAN Controller logs for entries that are related to Accepted publickey for vmanage-admin from unknown or unauthorized IP addresses.

Customers can also reach out to Cisco’s Technical Assistance Center for help in the investigation.

The company has also pushed out fixes for an information disclosure (CVE-2026-20224) and two privilege escalation vulnerabilities (CVE-2026-20209, CVE-2026-20210) affecting Cisco Catalyst SD-WAN Manager, but those are not known to have been exploited.

Cisco Talos researchers have published indicators of compromise and other information on ongoing attacks perpetrated by exploiting CVE-2026-20133, CVE-2026-20128, and CVE-2026-20122 in Cisco Catalyst SD-WAN Manager.

“The vast majority of observed exploitation attempts involved the use of the ZeroZenX Labs proof-of-concept code and accompanying JavaServer Pages (JSP) shell, which we are calling ‘XenShell.’ However, we observed several other JSP-based webshell variants,” the analysts shared.

“Following successful exploitation, the webshells would allow the attacker to execute bash commands on the affected system.”

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