Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
Moquette MQTT broker (io.moquette:moquette-broker) before 0.18.1 does not check write permissions when publishing Will messages for disconnected clients, so the ACL is bypassed for those messages. An unauthenticated attacker on a broker with anonymous access enabled (the default) can set a restricted topic as the Will topic and drop the TCP connection to inject messages into that topic. Upgrade to version 0.18.1. The source also describes a possible code execution impact on subscribers that deserialize message payloads, but it is not a broker-side effect.
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:H/A:N | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0057, the 47th percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:16 UTC First seen by agentprime
- 31 Oct 2026, 14:16 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-9jjc-fw8x-fmwx
- OSV: GHSA-9jjc-fw8x-fmwx
- github.com/moquette-io/moquette/security/advisories/GHSA-9jjc-fw8x-fmwx
- github.com/moquette-io/moquette/commit/e23df019f6a11e22c7d2047d4f86d07095466c97
- github.com/moquette-io/moquette/commit/f5a323fe782d1505c0097498cb22eb6ec6c96973
- github.com/moquette-io/moquette
- github.com/moquette-io/moquette/releases/tag/v0.18.1