Summary
Eclipse Milo vulnerable to Resource Exhaustion (Denial of Service)
Denial of Service
Details
OPC UA specification describes a concept named Subscriptions. Subscriptions monitor a set of Monitored Items for Notifications and return them to the Client in response to Publish requests. The server notifies the client about changes only in case the value is changed. Each monitored item is configured on a subscription, each subscription is linked to a single OPC UA session. Most OPC UA implementations set many controls and limitations for excessive memory consumption. For example:
- What is the maximum allowed number of concurrent sessions
- For each active sessions - what is the maximum allowed number of concurrent subscription per a single session
- For each active subscription - what is the maximum allowed number of concurrent monitored items per a single subscription
Clarity Research discovered a unique way to bypass those restrictions and fill up the OPC UA server process memory.
The close session request closes a connected session. A deleteSubscription flag is also sent in that message and determines whether the server should save the subscriptions for a future session reconnection or discard them upon session termination. If the deleteSubscription flag is False the server will store the subscriptions thus filling up the memory in an unlimited manner.
Sending multiple subscribe requests with multiple monitored items from multiple sessions will quickly fill up the process memory until the server crashes.
To trigger this bug all is needed is to create many sessions with subscriptions and monitored items without ever deleting the monitored items. Eventually these allocations will consume all the available process memory which will lead to a crash and denial of service condition.
Clarity PoC does:
while True:
Open a valid OPC UA session
Create multiple subscriptions
Add monitored items to each subscription
Close the session with the DeleteSubscriptions flag = False
Acknowledgement
We would like to thanks Vera Mens, Uri Katz, @sharonbrizinov of Team82 (Claroty Research) for this report.
For more information
If you have any questions or comments about this advisory:
- Open an issue in Eclipse Milo repository
- Email us at milo-dev
Impact
The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap. Typical impact: resource exhaustion leading to denial of service.
CVE-2022-25897 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.6.8); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2022-25897? CVE-2022-25897 is a high-severity allocation of resources without limits or throttling vulnerability in org.eclipse.milo:sdk-server (maven), affecting versions < 0.6.8. It is fixed in 0.6.8. The application allocates resources such as memory, threads, or file descriptors based on untrusted input without enforcing a cap.
- How severe is CVE-2022-25897? CVE-2022-25897 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of org.eclipse.milo:sdk-server are affected by CVE-2022-25897? org.eclipse.milo:sdk-server (maven) versions < 0.6.8 is affected.
- Is there a fix for CVE-2022-25897? Yes. CVE-2022-25897 is fixed in 0.6.8. Upgrade to this version or later.
- Is CVE-2022-25897 exploitable, and should I be worried? Whether CVE-2022-25897 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2022-25897 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2022-25897? Upgrade
org.eclipse.milo:sdk-serverto 0.6.8 or later.