diff --git a/reka-core/src/main/java/reka/modules/builtins/UnzipOperation.java b/reka-core/src/main/java/reka/modules/builtins/UnzipOperation.java
index 03d93374..00c4a3e8 100644
--- a/reka-core/src/main/java/reka/modules/builtins/UnzipOperation.java
+++ b/reka-core/src/main/java/reka/modules/builtins/UnzipOperation.java
@@ -6,6 +6,7 @@
 
 import java.io.ByteArrayInputStream;
 import java.io.FileOutputStream;
+import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.util.function.Function;
@@ -45,6 +46,9 @@ public void call(MutableData data, OperationContext ctx) {
 			ZipEntry e;
 			while ((e = zip.getNextEntry()) != null) {
 				java.nio.file.Path filepath = outputDir.resolve(e.getName());
+				if (!filepath.normalize().startsWith(outputDir.normalize())) {
+					throw new IOException("Bad zip entry");
+				}
 				Files.createDirectories(filepath.getParent());
 				FileOutputStream out = new FileOutputStream(filepath.toFile());
 				try {
diff --git a/reka-core/src/main/java/reka/util/Util.java b/reka-core/src/main/java/reka/util/Util.java
index b79eab6c..d5b2ea90 100644
--- a/reka-core/src/main/java/reka/util/Util.java
+++ b/reka-core/src/main/java/reka/util/Util.java
@@ -256,6 +256,9 @@ public static void unzip(byte[] bytes, java.nio.file.Path dest) {
 			ZipEntry e;
 			while ((e = zip.getNextEntry()) != null) {
 				java.nio.file.Path filepath = dest.resolve(e.getName());
+				if (!filepath.normalize().startsWith(dest.normalize())) {
+					throw new IOException("Bad zip entry");
+				}
 				Files.createDirectories(filepath.getParent());
 				FileOutputStream out = new FileOutputStream(filepath.toFile());
 				try {