GHSA-jxxm-27vp-c3m5
HIGHGHSA-jxxm-27vp-c3m5 is a high-severity (CVSS 7.1) CWE-863 vulnerability in github.com/nats-io/nats-server/v2. O3 Security confirms whether GHSA-jxxm-27vp-c3m5 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
NATS allows MQTT clients to bypass ACL checks
Blast Radius
github.com/nats-io/nats-server/v2🐹github.com/nats-io/nats-server/v2🐹github.com/nats-io/nats-serverReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Background
NATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing.
The nats-server provides an MQTT client interface.
Problem Description
When using ACLs on message subjects, these ACLs were not applied in the $MQTT.> namespace, allowing MQTT clients to bypass ACL checks for MQTT subjects.
Affected Versions
Any version before v2.12.6 or v2.11.15
Workarounds
None.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/nats-io/nats-server/v2 | all versions | 2.11.15 |
| 🐹Go | github.com/nats-io/nats-server/v2 | ≥ 2.12.0-RC.1&&< 2.12.6 | 2.12.6 |
| 🐹Go | github.com/nats-io/nats-server | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/nats-io/nats-server/v2. 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 github.com/nats-io/nats-server/v2 to 2.11.15 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-jxxm-27vp-c3m5 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-jxxm-27vp-c3m5 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-jxxm-27vp-c3m5. 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-jxxm-27vp-c3m5 in your dependencies?
O3 detects GHSA-jxxm-27vp-c3m5 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.