diff --git a/.gitignore b/.gitignore
index 97cca67..5691c92 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,3 +12,6 @@
 *.out
 
 .idea
+
+# go-mod cache
+vendor
\ No newline at end of file
diff --git a/cbc.go b/cbc.go
index a060f9e..fd4fdcf 100755
--- a/cbc.go
+++ b/cbc.go
@@ -2,6 +2,7 @@ package openssl
 
 import (
 	"crypto/cipher"
+	"errors"
 )
 
 // CBCEncrypt
@@ -11,6 +12,10 @@ func CBCEncrypt(block cipher.Block, src, iv []byte, padding string) ([]byte, err
 
 	encryptData := make([]byte, len(src))
 
+	if len(iv) != block.BlockSize() {
+		return nil, errors.New("CBCEncrypt: IV length must equal block size")
+	}
+
 	mode := cipher.NewCBCEncrypter(block, iv)
 	mode.CryptBlocks(encryptData, src)
 
@@ -22,6 +27,10 @@ func CBCDecrypt(block cipher.Block, src, iv []byte, padding string) ([]byte, err
 
 	dst := make([]byte, len(src))
 
+	if len(iv) != block.BlockSize() {
+		return nil, errors.New("CBCDecrypt: IV length must equal block size")
+	}
+
 	mode := cipher.NewCBCDecrypter(block, iv)
 	mode.CryptBlocks(dst, src)