CVE-2026-85724: Moquette Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-5f42-97gr-vfhq",
  "modified" : "2026-09-23T16:11:18Z",
  "published" : "2026-09-23T16:11:18Z",
  "aliases" : [ "CVE-2026-85724" ],
  "summary" : "Moquette: Pattern-ACL wildcard injection (cross-tenant authorization bypass) plus a remote-unauthenticated DoS cluster, a Will-message authorization bypass, and a cross-session durable-corruption bug",
  "details" : "moquette is reachable by untrusted MQTT clients (anonymous by default), so every byte from any client, including pre-authentication, is untrusted. This is a memory-safe JVM: the ceiling is authorization/ACL bypass + denial of service + cross-session integrity, **not RCE** (I did not find one and do not claim one). Audited at commit `da7f719a6bab9829d520b5838e13ea7b1f9be3ef`, module `broker/`.\n\n## What a connecting client can do\n\n1. (Critical) Bypass `pattern`-based ACLs across tenants. In `AuthorizationsCollector.canDoOperation` (AuthorizationsCollector.java:116-131, esp. line 123) the clientId/username is substituted raw into a pattern ACL rule and then wildcard-matched, and the clientId is never validated for MQTT wildcard characters +/# at CONNECT (MQTTConnection.processConnect):\n\nTopic substitutedTopic = new Topic(auth.topic.toString().replace(\"%c\", client).replace(\"%u\", username));\nif (topic.match(substitutedTopic)) return true;\n\nA client that connects with clientId + turns sensor/%c/# into the filter sensor/+/#, gaining cross-tenant read AND write. (Precondition: pattern ACL rules configured — a common multi-tenant setup.)\n\n2. (High) Crash the whole broker. SessionEventLoop (SessionEventLoop.java:40-54) catches only InterruptedException and is never restarted (SessionEventLoopGroup), so any uncaught exception on it wedges every co-located client. Trivially reachable inputs: malformed $share/grp SUBSCRIBE (SharedSubscriptionUtils.extractShareName -> StringIndexOutOfBoundsException), deeply nested topic (CTrie recursion -> StackOverflowError), and ACL NPE below. Unbounded subscriptions / retained / in-flight / topic-alias / interceptor state (BrokerInterceptor uses an unbounded queue) also allow OOM; durable stores allow disk exhaustion.\n\n3. (High) NPE in ACL sink on clientId # (invalid filter sensor/#/# -> null tokens -> Topic.match NPE at Topic.java:173).\n\n4. (High) Will-message authorization bypass. Last-Will topic is published (PostOffice.publishWill) without canWrite/reserved-topic checks used for normal PUBLISH.\n\n5. (Medium) Cross-session durable corruption. H2PersistentQueue opens queue_\"+clientId and queue_\"+clientId+\"_meta; client id sensor_meta collides with victim sensor metadata map -> corrupts head/tail.\n\n6. (Medium) Fail-open if authenticator/authorizator class fails to load -> PermitAll/AcceptAll (Server.java:483-531).\n\n## Proof of concept\n\nSource-only, no network; PoCs run on JDK 17:\n- PoCPatternAcl — clientId + gains cross-tenant read/write; clientId # triggers NPE\n- PoCSharedSubCrash — extractShareName(\"$share/grp\") throws StringIndexOutOfBoundsException\n- PoCMapCollision — H2 MVStore collision overwrites victim metadata pointer\n\n## Impact\n\nCross-tenant eavesdropping and injection, whole-broker DoS, unauthorized Will publishes, and cross-session durable corruption.\n\n## Remediation\n\n1. Reject clientId/username containing +/# (and / if structural) at CONNECT; expand %c/%u as literal tokens.\n2. Harden SessionEventLoop (catch Throwable + restart supervision) and validate $share filters.\n3. Apply authorization to Will publishes like normal PUBLISH.\n4. Add resource caps (connections, queues, retained, aliases, interceptor queue) + bounded session expiry.\n5. Separate H2 namespaces and fail closed on auth-class load failure.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.moquette:moquette-broker"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.18.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.18.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/security/advisories/GHSA-5f42-97gr-vfhq"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/pull/957"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/pull/958"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/pull/959"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/commit/14a2f4fd280c8f6a791600c306cbccecb7c67007"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/commit/26498631e92d50440b4e3ed42fa546253cc4090c"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/commit/72d6c8257191d2e4b2e3aa11ab25fd09f88c6cb7"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/commit/86feb7c31e6fac849c465d8079d08c0e7ef01cdf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/commit/affdc71fdba92dc020421678970ae70518fb6da2"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/commit/b4a98bb3f3425ece476ed073aa080c627c1239af"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/commit/c65b3e90fa03e562e2c2fa69c3ee916c2cbfbd2b"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/commit/ca17e0be19e86d5e291f4532dfdc94616c8e0049"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/commit/d77753542e262b7aa573dee3c2b05e44439bbd96"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/commit/f5a323fe782d1505c0097498cb22eb6ec6c96973"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/moquette-io/moquette"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/moquette-io/moquette/releases/tag/v0.18.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-23T16:11:18Z",
    "nvd_published_at" : null
  }
}