diff --git a/modules/objdetect/src/aruco/aruco_dictionary.cpp b/modules/objdetect/src/aruco/aruco_dictionary.cpp
index 3e975c00bf..3779e3fb94 100644
--- a/modules/objdetect/src/aruco/aruco_dictionary.cpp
+++ b/modules/objdetect/src/aruco/aruco_dictionary.cpp
@@ -109,6 +109,8 @@ bool Dictionary::readDictionary(const cv::FileNode& fn) {
     int nMarkers = 0, _markerSize = 0;
     if (fn.empty() || !readParameter("nmarkers", nMarkers, fn) || !readParameter("markersize", _markerSize, fn))
         return false;
+    if (_markerSize <= 0)
+        return false;
     Mat bytes(0, 0, CV_8UC1), marker(_markerSize, _markerSize, CV_8UC1);
     std::string markerString;
     for (int i = 0; i < nMarkers; i++) {
@@ -116,6 +118,8 @@ bool Dictionary::readDictionary(const cv::FileNode& fn) {
         ostr << i;
         if (!readParameter("marker_" + ostr.str(), markerString, fn))
             return false;
+        if (markerString.size() != (size_t)_markerSize * _markerSize)
+            return false;
         for (int j = 0; j < (int) markerString.size(); j++)
             marker.at<unsigned char>(j) = (markerString[j] == '0') ? 0 : 1;
         bytes.push_back(Dictionary::getByteListFromBits(marker));
diff --git a/modules/objdetect/test/test_arucodetection.cpp b/modules/objdetect/test/test_arucodetection.cpp
index 53f4302cc0..8b850eda1f 100644
--- a/modules/objdetect/test/test_arucodetection.cpp
+++ b/modules/objdetect/test/test_arucodetection.cpp
@@ -1409,6 +1409,46 @@ TEST(CV_ArucoMultiDict, serialization)
 }
 
 
+TEST(CV_ArucoDictionary, readDictionary_oversized_marker)
+{
+    // A marker string longer than markersize*markersize must be rejected instead of
+    // being written past the markersize x markersize buffer in readDictionary.
+    std::string serialized;
+    {
+        FileStorage fs_out(".json", FileStorage::WRITE + FileStorage::MEMORY);
+        ASSERT_TRUE(fs_out.isOpened());
+        fs_out << "nmarkers" << 1;
+        fs_out << "markersize" << 5;
+        fs_out << "marker_0" << std::string(2000, '1');
+        serialized = fs_out.releaseAndGetString();
+    }
+    FileStorage fs_in(serialized, FileStorage::READ + FileStorage::MEMORY);
+    ASSERT_TRUE(fs_in.isOpened());
+    aruco::Dictionary dict;
+    bool ok = true;
+    ASSERT_NO_THROW(ok = dict.readDictionary(fs_in.root()));
+    EXPECT_FALSE(ok);
+}
+
+
+TEST(CV_ArucoDictionary, readDictionary_roundtrip)
+{
+    aruco::Dictionary dict = aruco::getPredefinedDictionary(aruco::DICT_5X5_50);
+    std::string serialized;
+    {
+        FileStorage fs_out(".json", FileStorage::WRITE + FileStorage::MEMORY);
+        ASSERT_TRUE(fs_out.isOpened());
+        dict.writeDictionary(fs_out);
+        serialized = fs_out.releaseAndGetString();
+    }
+    FileStorage fs_in(serialized, FileStorage::READ + FileStorage::MEMORY);
+    ASSERT_TRUE(fs_in.isOpened());
+    aruco::Dictionary loaded;
+    ASSERT_TRUE(loaded.readDictionary(fs_in.root()));
+    EXPECT_EQ(dict, loaded);
+}
+
+
 struct ArucoThreading: public testing::TestWithParam<aruco::CornerRefineMethod>
 {
     struct NumThreadsSetter {