diff --git a/Lib/test/test_memoryview.py b/Lib/test/test_memoryview.py
index 656318668e6d6e..0203779d994a3d 100644
--- a/Lib/test/test_memoryview.py
+++ b/Lib/test/test_memoryview.py
@@ -228,6 +228,32 @@ def test_compare(self):
                 self.assertRaises(TypeError, lambda: m >= c)
                 self.assertRaises(TypeError, lambda: c > m)
 
+    def test_compare_1d_concurrent_mutation(self):
+        # Prevent crashes during a mixed format 1-D comparison loop.
+        # Regression test for https://github.com/python/cpython/issues/142663.
+        src1 = array.array("d", [1.0, 2.0])
+        src2 = array.array("l", [1, 2])
+        mv1, mv2 = memoryview(src1), memoryview(src2)
+        self.do_test_compare_concurrent_mutation(src1, mv1, mv2)
+
+    def test_compare_2d_concurrent_mutation(self):
+        # Prevent crashes during a mixed format 2-D comparison loop.
+        # Regression test for https://github.com/python/cpython/issues/142663.
+        src1 = array.array("d", [1.0, 2.0])
+        src2 = array.array("l", [1, 2])
+        mv1 = memoryview(src1).cast("B").cast("d", shape=(1, 2))
+        mv2 = memoryview(src2).cast("B").cast("l", shape=(1, 2))
+        self.do_test_compare_concurrent_mutation(src1, mv1, mv2)
+
+    def do_test_compare_concurrent_mutation(self, src1, mv1, mv2):
+        class S(struct.Struct):
+            def unpack_from(self, buf, /, offset=0):
+                mv1.release()
+                src1.append(3.14)
+                return (1,)
+        with support.swap_attr(struct, "Struct", S):
+            self.assertRaises(BufferError, mv1.__eq__, mv2)
+
     def check_attributes_with_type(self, tp):
         m = self._view(tp(self._source))
         self.assertEqual(m.format, self.format)
diff --git a/Misc/NEWS.d/next/Library/2025-12-30-22-12-27.gh-issue-142663.gq7iIf.rst b/Misc/NEWS.d/next/Library/2025-12-30-22-12-27.gh-issue-142663.gq7iIf.rst
new file mode 100644
index 00000000000000..39ee1ef29267a7
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-12-30-22-12-27.gh-issue-142663.gq7iIf.rst
@@ -0,0 +1,2 @@
+Fix use-after-free crashes when a :class:`memoryview` is mutated
+during a comparison with another object.
diff --git a/Objects/memoryobject.c b/Objects/memoryobject.c
index f3b7e4a396b4a1..16b8495659c0d8 100644
--- a/Objects/memoryobject.c
+++ b/Objects/memoryobject.c
@@ -3122,7 +3122,8 @@ memory_richcompare(PyObject *v, PyObject *w, int op)
     }
     vv = VIEW_ADDR(v);
 
-    if (PyMemoryView_Check(w)) {
+    int w_is_mv = PyMemoryView_Check(w);
+    if (w_is_mv) {
         if (BASE_INACCESSIBLE(w)) {
             equal = (v == w);
             goto result;
@@ -3165,6 +3166,13 @@ memory_richcompare(PyObject *v, PyObject *w, int op)
             goto result;
         }
     }
+    /* Prevent memoryview object from being released and its underlying buffer
+       reshaped during a mixed format comparison loop. */
+    // See https://github.com/python/cpython/issues/142663.
+    ((PyMemoryViewObject *)v)->exports++;
+    if (w_is_mv) {
+        ((PyMemoryViewObject *)w)->exports++;
+    }
 
     if (vv->ndim == 0) {
         equal = unpack_cmp(vv->buf, ww->buf,
@@ -3183,6 +3191,11 @@ memory_richcompare(PyObject *v, PyObject *w, int op)
                         vfmt, unpack_v, unpack_w);
     }
 
+    ((PyMemoryViewObject *)v)->exports--;
+    if (w_is_mv) {
+        ((PyMemoryViewObject *)w)->exports--;
+    }
+
 result:
     if (equal < 0) {
         if (equal == MV_COMPARE_NOT_IMPL)