Merge pull request #28250 from satyam102006:fix/stackblur-overflow-28233

imgproc: fix heap-buffer-overflow in stackBlur #28233 #28250

### Summary
Fixes a heap-buffer-overflow in `cv::stackBlur` when the kernel size is larger than the image dimensions 
### Changes
* Added input validation to clamp the kernel size to the image dimensions.
* Added a regression test (`regression_28233`) covering 1x1 and small image cases.

Fixes #28233

modules/imgproc/src/stackblur.cpp

@@ -41,6 +41,7 @@ OTHER DEALINGS IN THE SOFTWARE.
 #include "opencv2/core/hal/intrin.hpp"
 
 #include <iostream>
+#include <algorithm>
 
 using namespace std;
 
@@ -1199,12 +1200,17 @@ void stackBlur(InputArray _src, OutputArray _dst, Size ksize)
     CV_Assert( ksize.width  > 0 && ksize.width  % 2 == 1 &&
                ksize.height > 0 && ksize.height % 2 == 1 );
 
-    int radiusH = ksize.height / 2;
-    int radiusW = ksize.width / 2;
-
     int stype = _src.type(), sdepth = _src.depth();
     Mat src = _src.getMat();
 
+    if (ksize.width > src.cols)
+        ksize.width = (src.cols % 2 == 0) ? std::max(1, src.cols - 1) : src.cols;
+    if (ksize.height > src.rows)
+        ksize.height = (src.rows % 2 == 0) ? std::max(1, src.rows - 1) : src.rows;
+
+    int radiusH = ksize.height / 2;
+    int radiusW = ksize.width / 2;
+
     if (ksize.width == 1)
     {
         _src.copyTo(_dst);

modules/imgproc/test/test_stackblur.cpp

@@ -311,5 +311,18 @@ TEST_P(StackBlur_GaussianBlur, compare)
 }
 
 INSTANTIATE_TEST_CASE_P(Imgproc, StackBlur_GaussianBlur, testing::Values(CV_8U, CV_16S, CV_16U, CV_32F));
+
+TEST(Imgproc_StackBlur, regression_28233)
+{
+    Mat src1(1, 1, CV_8UC1, Scalar(123));
+    Mat dst1;
+    EXPECT_NO_THROW(stackBlur(src1, dst1, Size(9, 1)));
+    EXPECT_EQ(dst1.at<uchar>(0, 0), 123);
+
+    Mat src2(3, 3, CV_8UC1, Scalar(50));
+    Mat dst2;
+    EXPECT_NO_THROW(stackBlur(src2, dst2, Size(11, 11)));
+    EXPECT_EQ(dst2.at<uchar>(1, 1), 50);
+}
 }
 }

modules/js/test/test_imgproc.js

@@ -552,7 +552,7 @@ QUnit.test('test_filter', function(assert) {
         cv.stackBlur(src, src, new cv.Size(3, 3));
 
         // Verify result.
-        let expected = new Uint8Array([22,29,36,38,43,50]);
+        let expected = new Uint8Array([14,22,29,46,51,58]);
 
         assert.deepEqual(src.data, expected);
         src.delete();