GHSA-fph9-f5r6-vhqf
HIGHEclipse Milo vulnerable to Resource Exhaustion (Denial of Service)
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
org.eclipse.milo:sdk-serverReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Impact
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
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.eclipse.milo:sdk-server | all versions | 0.6.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.eclipse.milo:sdk-server. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.eclipse.milo:sdk-server to 0.6.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fph9-f5r6-vhqf is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-fph9-f5r6-vhqf is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-fph9-f5r6-vhqf. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-fph9-f5r6-vhqf in your dependencies?
O3 detects GHSA-fph9-f5r6-vhqf across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.