Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
NATS server (github.com/nats-io/nats-server/v2) versions before 2.11.15, and 2.12.0-RC.1 up to but not including 2.12.6, are vulnerable. A client that can reach the leafnode port can crash the server before authenticating by sending a malformed message. Upgrade to 2.11.15 or 2.12.6. If you do not need leafnode support, disable it, or restrict network access to the leafnode port.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 7.5 | High | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0063, the 50th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:13 UTC First seen by agentprime
- 31 Oct 2026, 14:13 UTC Confirmed by OSV