diff --git a/PyPDF2/_encryption.py b/PyPDF2/_encryption.py
index 0eae5c4ff..f1302a3a3 100644
--- a/PyPDF2/_encryption.py
+++ b/PyPDF2/_encryption.py
@@ -84,6 +84,9 @@ def decrypt(self, data: bytes) -> bytes:
             iv = data[:16]
             data = data[16:]
             aes = AES.new(self.key, AES.MODE_CBC, iv)
+            if len(data) % 16:
+                from Crypto.Util.Padding import pad
+                data = pad(data, 16)
             d = aes.decrypt(data)
             if len(d) == 0:
                 return d