func TestInvalidPaddingOpen(t *testing.T) {
	key := make([]byte, 32)
	nonce := make([]byte, 16)

	// Plaintext with invalid padding
	plaintext := padBuffer(make([]byte, 28), aes.BlockSize)
	plaintext[len(plaintext)-1] = 0xFF

	io.ReadFull(rand.Reader, key)
	io.ReadFull(rand.Reader, nonce)

	block, _ := aes.NewCipher(key)
	cbc := cipher.NewCBCEncrypter(block, nonce)
	buffer := append([]byte{}, plaintext...)
	cbc.CryptBlocks(buffer, buffer)

	aead, _ := NewCBCHMAC(key, aes.NewCipher)
	ctx := aead.(*cbcAEAD)

	// Mutated ciphertext, but with correct auth tag
	size := len(buffer)
	ciphertext, tail := resize(buffer, size+(len(key)/2))
	copy(tail, ctx.computeAuthTag(nil, nonce, ciphertext[:size]))

	// Open should fail (b/c of invalid padding, even though tag matches)
	_, err := aead.Open(nil, nonce, ciphertext, nil)
	if err == nil || !strings.Contains(err.Error(), "invalid padding") {
		t.Error("no or unexpected error on open with invalid padding:", err)
	}
}
The software performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control.