From 51e23ea7fd49cb04ba33db3bfbeba690a2f7c5b4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Dr=2E=20Lars=20V=C3=B6lker?=
 <lars.voelker@technica-engineering.de>
Date: Fri, 3 Feb 2023 19:42:03 +0100
Subject: [PATCH] ISO15765/ISO10681 memory corruption bugfix

Fixes a situation in which the code wrote behind the frag_id_high array
and corrupted memory.

Closes #18839
---
 epan/dissectors/packet-iso10681.c | 7 ++++++-
 epan/dissectors/packet-iso15765.c | 8 ++++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/epan/dissectors/packet-iso10681.c b/epan/dissectors/packet-iso10681.c
index 9e749eea8cf..6772e936e06 100644
--- a/epan/dissectors/packet-iso10681.c
+++ b/epan/dissectors/packet-iso10681.c
@@ -340,7 +340,12 @@ dissect_iso10681(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32 fr
             }
 
             if (!(pinfo->fd->visited)) {
-                frag_id += ((iso10681_frame->frag_id_high[frag_id]++) * 16);
+                DISSECTOR_ASSERT(frag_id < 16);
+                guint16 tmp = iso10681_frame->frag_id_high[frag_id]++;
+                /* Make sure that we assert on using more than 4096 (16*255) segments.*/
+                DISSECTOR_ASSERT(iso10681_frame->frag_id_high[frag_id] != 0);
+                frag_id += tmp * 16;
+
                 /* Save the frag_id for subsequent dissection */
                 iso10681_info->frag_id = frag_id;
             }
diff --git a/epan/dissectors/packet-iso15765.c b/epan/dissectors/packet-iso15765.c
index 3157397bf21..4c73927c807 100644
--- a/epan/dissectors/packet-iso15765.c
+++ b/epan/dissectors/packet-iso15765.c
@@ -573,14 +573,18 @@ dissect_iso15765(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint32 bu
         tvbuff_t *new_tvb = NULL;
         iso15765_frame_t *iso15765_frame;
         guint16 frag_id = frag_id_low;
-
         /* Get frame information */
         iso15765_frame = (iso15765_frame_t *)wmem_map_lookup(iso15765_frame_table,
                                                              GUINT_TO_POINTER(iso15765_info->seq));
 
         if (iso15765_frame != NULL) {
             if (!(pinfo->fd->visited)) {
-                frag_id += ((iso15765_frame->frag_id_high[frag_id]++) * 16);
+                DISSECTOR_ASSERT(frag_id < 16);
+                guint16 tmp = iso15765_frame->frag_id_high[frag_id]++;
+                /* Make sure that we assert on using more than 4096 (16*255) segments.*/
+                DISSECTOR_ASSERT(iso15765_frame->frag_id_high[frag_id] != 0);
+                frag_id += tmp * 16;
+
                 /* Save the frag_id for subsequent dissection */
                 iso15765_info->frag_id = frag_id;
 
-- 
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