CISA Warns of Six Eclipse Milo OPC UA Flaws
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Six vulnerabilities in Eclipse Milo OPC UA stack through 1.1.4 allow authorization bypass, credential theft, DoS, and info disclosure; upgrade to 1.1.5.
CISA published an ICS advisory for Eclipse Foundation's Eclipse Milo, an open-source OPC UA stack used across chemical, critical manufacturing, energy, and water/wastewater sectors worldwide. The advisory details six distinct CVEs affecting versions 0.6.0 through 1.1.4, covering authorization bypass via batched Call service requests, a padding-oracle attack against Basic128Rsa15-encrypted username tokens that can recover victim passwords, missing authorization on diagnostics nodes exposing session usernames and credentials-related metadata, a RoleMapper configuration flaw that silently disables role-permission checks for anonymous sessions, and two denial-of-service issues — one from unreleased memory on disconnected UASC channels and another from exception-unsafe monitored-item quota accounting exploitable via deeply nested PubSub ExtensionObjects causing a StackOverflowError.
Collectively these flaws let low-privileged or anonymous OPC UA clients execute denied methods, read or delete protected nodes, recover other users' credentials and impersonate them, or exhaust server resources to deny service to all clients until restart. No in-the-wild exploitation is noted in the advisory; it was reported to CISA by researcher Abhinav Agarwal. The Eclipse Foundation has fixed all issues in Milo 1.1.5; there is no patched 0.6.x release, so organizations on that branch must migrate to 1.1.5 or later. CISA additionally recommends standard ICS network hygiene: minimizing internet exposure of control system devices, isolating OPC UA servers behind firewalls, and using VPNs for any required remote access.
Defenders running Eclipse Milo-based OPC UA servers should prioritize upgrading to 1.1.5, audit RoleMapper and diagnostics-node configurations for unintended anonymous access, and monitor for abnormal ActivateSession request patterns that could indicate padding-oracle probing or repeated incomplete-chunk connections consistent with the memory-exhaustion DoS.
Mentioned in this report
Source reporting: https://www.cisa.gov/news-events/ics-advisories/icsa-26-288-01
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