# CVE-2026-98401: net: iptunnel: fix stale transport header during tunnel decapsulation CVE-2026-98401 is fixed in 38 products on 1 platform, first by DEBIAN-CVE-2026-98401, released October 16, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-98401 - Priority: High - CVSS: 7.5 (Moderate) - EPSS: 0.0060 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Oct 12, 2026 - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98401 ## Description In the Linux kernel, the following vulnerability has been resolved: net: iptunnel: fix stale transport header during tunnel decapsulation Syzbot reported a crash in qdisc_pkt_len_segs_init() caused by a stale transport_header offset after tunnel decapsulation. BUG: unable to handle page fault for address: ffffed102091a42e Oops: Oops: 0000 [#1] SMP KASAN NOPTI CPU: 0 UID: 0 PID: 340 Comm: qdisc_uaf_repro Not tainted 7.2.0-rc4-00061-g248951ddc14d #256 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:__asan_load2 qdisc_pkt_len_segs_init (net/core/dev.c:4145) __dev_queue_xmit (net/core/dev.c:4787) br_dev_queue_push_xmit (net/bridge/br_forward.c:53) br_handle_frame_finish (net/bridge/br_input.c:229) br_handle_frame (net/bridge/br_input.c:315) __netif_receive_skb_core.constprop.0 (net/core/dev.c:6099) __netif_receive_skb_list_core (net/core/dev.c:6287) netif_receive_skb_list_internal (net/core/dev.c:6445) napi_complete_done (net/core/dev.c:6813) gro_cell_poll (net/core/gro_cells.c:74) __napi_poll (net/core/dev.c:7735) net_rx_action (net/core/dev.c:7798 net/core/dev.c:7955) handle_softirqs (kernel/softirq.c:622) do_softirq (kernel/softirq.c:523 kernel/softirq.c:510 ) __local_bh_enable_ip (kernel/softirq.c:450) tun_get_user (drivers/net/tun.c:1986 (discriminator 1)) tun_chr_write_iter (drivers/net/tun.c:2032) The issue is completely latent until qdisc read transport header in commit 7fb4c1967011 ("net: pull headers in qdisc_pkt_len_segs_init()"). The crash requires four conditions to line up: 1. The incoming packet is encapsulated and carries GSO metadata. The outer transport header offset is stored in skb->transport_header while the packet is still in the outer tunnel context. 2. The tunnel receiver strips the outer headers. skb->data is advanced to the inner frame, but skb->transport_header is left pointing to the now-removed outer L4 header, so it becomes a negative offset relative to the new data. 3. The inner frame is not delivered to the local IP stack. Instead, it is forwarded at L2 by a bridge or HSR, so ip_rcv_core() never runs and the transport header is not reset to the inner L4 offset. 4. The forwarding path calls __dev_queue_xmit(), which enters qdisc_pkt_len_segs_init(). That function computes the GSO header length from skb_transport_offset(skb). Because the offset is negative, the unsigned cast overflows and pskb_may_pull(skb, hdr_len + sizeof(struct tcphdr)) reads past the end of the skb, triggering a KASAN fault or page fault. The issue specifically requires GSO packets (shinfo->gso_size != 0), which are processed/aggregated through gro_cells. Fix this by clearing transport_header to the ~0U sentinel in gro_cell for all tunnnel driver. GTP does not support GRO/GSO, drop the evil GSO packets in GTP directly. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | bpftool6.12 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | bpftool6.12-debuginfo amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | bpftool6.18 amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | bpftool6.18-debuginfo amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel-livepatch-6.12.111-136.204 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel-livepatch-6.18.54-121.166 amzn 2023 | 1:1.0-0.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.12 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.12-debuginfo amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.12-debuginfo-common-aarch64 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.12-debuginfo-common-x86_64 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.12-devel amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.12-headers amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.12-modules-extra amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.12-modules-extra-common amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.12-tools amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.12-tools-debuginfo amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.12-tools-devel amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | kernel6.18 amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.18-debuginfo amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.18-debuginfo-common-aarch64 amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.18-debuginfo-common-x86_64 amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.18-devel amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.18-headers amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.18-modules-extra amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.18-modules-extra-common amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.18-tools amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.18-tools-debuginfo amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | kernel6.18-tools-devel amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | linux Debian 13.5 (trixie) | 6.12.111-1 | [DEBIAN-CVE-2026-98401](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98401.md) | Oct 16, 2026 | | Linux | linux Debian 14 | 7.2.7-1 | [DEBIAN-CVE-2026-98401](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98401.md) | Oct 16, 2026 | | Linux | microvm-kernel6.18 amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | perf6.12 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | perf6.12-debuginfo amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | perf6.18 amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | perf6.18-debuginfo amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | python3-perf6.12 amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | python3-perf6.12-debuginfo amzn 2023 | 1:6.12.111-136.204.amzn2023 | [ALAS2023-2026-3193](https://patchblox.com/security/data/fix/linux/alas2023-2026-3193.md) | Nov 7, 2026 | | Linux | python3-perf6.18 amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | | Linux | python3-perf6.18-debuginfo amzn 2023 | 1:6.18.54-121.166.amzn2023 | [ALAS2023-2026-3192](https://patchblox.com/security/data/fix/linux/alas2023-2026-3192.md) | Nov 7, 2026 | --- Data as of 2026-11-08T06:59:42Z UTC. 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