core: FileStorage: detect invalid attribute value

modules/core/src/persistence_xml.cpp

@@ -737,6 +737,8 @@ public:
                 if( c != '\"' && c != '\'' )
                 {
                     ptr = skipSpaces( ptr, CV_XML_INSIDE_TAG );
+                    if(!ptr)
+                        CV_PARSE_ERROR_CPP("Invalid attribute value");
                     if( *ptr != '\"' && *ptr != '\'' )
                         CV_PARSE_ERROR_CPP( "Attribute value should be put into single or double quotes" );
                 }

modules/core/test/test_io.cpp

@@ -1985,4 +1985,22 @@ INSTANTIATE_TEST_CASE_P( /*nothing*/,
     Core_InputOutput_regression_25073,
     Values("test.json", "test.xml", "test.yml") );
 
+// see https://github.com/opencv/opencv/issues/25946
+TEST(Core_InputOutput, FileStorage_invalid_attribute_value_regression_25946)
+{
+    const std::string fileName = cv::tempfile("FileStorage_invalid_attribute_value_exception_test.xml");
+    const std::string content = "<?xml \n_=";
+
+    std::fstream testFile;
+    testFile.open(fileName.c_str(), std::fstream::out);
+    if(!testFile.is_open()) FAIL();
+    testFile << content;
+    testFile.close();
+
+    FileStorage fs;
+    EXPECT_ANY_THROW( fs.open(fileName, FileStorage::READ + FileStorage::FORMAT_XML) );
+
+    ASSERT_EQ(0, std::remove(fileName.c_str()));
+}
+
 }} // namespace