diff -rupN --no-dereference openjpeg-2.3.1/src/lib/openjp2/t2.c openjpeg-2.3.1-new/src/lib/openjp2/t2.c
--- openjpeg-2.3.1/src/lib/openjp2/t2.c	2020-12-17 16:25:45.009030263 +0100
+++ openjpeg-2.3.1-new/src/lib/openjp2/t2.c	2020-12-17 16:25:45.011030261 +0100
@@ -787,6 +787,15 @@ static OPJ_BOOL opj_t2_encode_packet(OPJ
             continue;
         }
 
+        /* Avoid out of bounds access of https://github.com/uclouvain/openjpeg/issues/1297 */
+        /* but likely not a proper fix. */
+        if (precno >= res->pw * res->ph) {
+            opj_event_msg(p_manager, EVT_ERROR,
+                          "opj_t2_encode_packet(): accessing precno=%u >= %u\n",
+                          precno, res->pw * res->ph);
+            return OPJ_FALSE;
+        }
+
         prc = &band->precincts[precno];
         l_nb_blocks = prc->cw * prc->ch;
         cblk = prc->cblks.enc;