CVE-2026-77406: RabbitMQ amqp091-go Consumer Message Flooding Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-rm6m-hrcw-jw33",
  "modified" : "2026-09-17T17:04:05Z",
  "published" : "2026-09-17T17:04:05Z",
  "aliases" : [ "CVE-2026-77406" ],
  "summary" : "RabbitMQ amqp091-go: Consumer Message Flooding via Signed-to-Unsigned Integer Casting in Qos Configuration",
  "details" : "## Summary\nA logic and resource exhaustion vulnerability exists in the AMQP client's Quality of Service (`Qos`) configuration method. The `Qos` function accepts signed integers (`int`) for the `prefetchCount` and `prefetchSize` parameters but casts them directly to unsigned integers (`uint16` and `uint32`, respectively) when formatting the wire-level frame.\n\nIf a developer passes a negative integer (such as `-1`) to these parameters—frequently intended as a sentinel value meaning \"no change\" or \"no limit\"—the application performs an implicit signed-to-unsigned conversion. This wraps the values to their absolute maximum limit ($65535$ and $4294967295$). Consequently, a consumer expecting restricted message delivery rates is suddenly flooded with an unlimited volume of messages, potentially exhausting memory resources and crashing the application.\n\n---\n\n## Vulnerability Details\n\n### Mechanism\nThe bug manifests during the structural assignment inside the channel's `Qos` method:\n\n```go\n// channel.go:795-796\nPrefetchCount: uint16(prefetchCount),  // -1 wraps to 65535\nPrefetchSize:  uint32(prefetchSize),   // -1 wraps to 4294967295\n```\n\nIn Go, converting a negative signed integer to an unsigned integer shifts the value via two's complement arithmetic. Because no boundary validation or signedness check occurs prior to the cast:\n* Passing `-1` for `prefetchCount` yields a wire value of `65535`.\n* Passing `-1` for `prefetchSize` yields a wire value of `4294967295`.\n\n### Impact\nThe AMQP broker interprets a `prefetch-count` of `65535` as an instruction to dispatch messages to the consumer with virtually no concurrency limits. \n\nIf the application is processing heavy payloads or relies on strict rate-limiting to maintain stability, this unexpected flood will cause rapid heap memory growth, unmanageable processing queues, and an eventual Out-Of-Memory (OOM) termination.\n\n---\n\n## Attack Vector\nAn attacker who can manipulate configuration files, environmental variables, or API inputs that dictate client Qos settings can trigger an application-layer Denial of Service:\n\n1. **Malicious Input:** An attacker sets a service's prefetch configuration parameter to `-1`.\n2. **Implicit Overflow:** The application initializes the channel, executes `Qos(-1, ...)`, and transmits an unintended maximum-capacity request to the RabbitMQ/AMQP broker.\n3. **Consumer Exhaustion:** The broker flushes the entire contents of the queue directly into the client consumer's network buffer, bypassing expected application concurrency barriers and inducing a crash.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/rabbitmq/amqp091-go"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.13.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/rabbitmq/amqp091-go/security/advisories/GHSA-rm6m-hrcw-jw33"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-77406"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rabbitmq/amqp091-go/pull/351"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rabbitmq/amqp091-go/commit/3b879e1d1d25b544e26b3bc3d7db3213203c0f3b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/rabbitmq/amqp091-go"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/rabbitmq/amqp091-go/releases/tag/v1.13.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-195" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-17T17:04:05Z",
    "nvd_published_at" : "2026-09-16T15:17:49Z"
  }
}