In the Linux kernel, the following vulnerability has been resolved:
ipv6: ensure sane device mtu in tunnels
Another syzbot report [1] with no reproducer hints at a bug in ip6_gre tunnel (dev:ip6gretap0)
Since ipv6 mcast code makes sure to read dev->mtu once and applies a sanity check on it (see commit b9b312a7a451 "ipv6: mcast: better catch silly mtu values"), a remaining possibility is that a layer is able to set dev->mtu to an underflowed value (high order bit set).
This could happen indeed in ip6gre_tnl_link_config_route(), ip6_tnl_link_config() and ipip6_tunnel_bind_dev()
Make sure to sanitize mtu value in a local variable before it is written once on dev->mtu, as lockless readers could catch wrong temporary value.
[1] skbuff: skb_over_panic: text:ffff80000b7a2f38 len:40 put:40 head:ffff000149dcf200 data:ffff000149dcf2b0 tail:0xd8 end:0xc0 dev:ip6gretap0 ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:120 Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP Modules linked in: CPU: 1 PID: 10241 Comm: kworker/1:1 Not tainted 6.0.0-rc7-syzkaller-18095-gbbed346d5a96 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/30/2022 Workqueue: mld mld_ifc_work pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : skb_panic+0x4c/0x50 net/core/skbuff.c:116 lr : skb_panic+0x4c/0x50 net/core/skbuff.c:116 sp : ffff800020dd3b60 x29: ffff800020dd3b70 x28: 0000000000000000 x27: ffff00010df2a800 x26: 00000000000000c0 x25: 00000000000000b0 x24: ffff000149dcf200 x23: 00000000000000c0 x22: 00000000000000d8 x21: ffff80000b7a2f38 x20: ffff00014c2f7800 x19: 0000000000000028 x18: 00000000000001a9 x17: 0000000000000000 x16: ffff80000db49158 x15: ffff000113bf1a80 x14: 0000000000000000 x13: 00000000ffffffff x12: ffff000113bf1a80 x11: ff808000081c0d5c x10: 0000000000000000 x9 : 73f125dc5c63ba00 x8 : 73f125dc5c63ba00 x7 : ffff800008161d1c x6 : 0000000000000000 x5 : 0000000000000080 x4 : 0000000000000001 x3 : 0000000000000000 x2 : ffff0001fefddcd0 x1 : 0000000100000000 x0 : 0000000000000089 Call trace: skb_panic+0x4c/0x50 net/core/skbuff.c:116 skb_over_panic net/core/skbuff.c:125 [inline] skb_put+0xd4/0xdc net/core/skbuff.c:2049 ip6_mc_hdr net/ipv6/mcast.c:1714 [inline] mld_newpack+0x14c/0x270 net/ipv6/mcast.c:1765 add_grhead net/ipv6/mcast.c:1851 [inline] add_grec+0xa20/0xae0 net/ipv6/mcast.c:1989 mld_send_cr+0x438/0x5a8 net/ipv6/mcast.c:2115 mld_ifc_work+0x38/0x290 net/ipv6/mcast.c:2653 process_one_work+0x2d8/0x504 kernel/workqueue.c:2289 worker_thread+0x340/0x610 kernel/workqueue.c:2436 kthread+0x12c/0x158 kernel/kthread.c:376 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860 Code: 91011400 aa0803e1 a90027ea 94373093 (d4210000)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade kernel-debuginfoUpgrade kernel-debuginfo-common-aarch64Upgrade perf-debuginfoUpgrade kernel-develUpgrade kernel-tools-debuginfoUpgrade kernel-tools-develUpgrade bpftoolUpgrade kernel-livepatch-5.10.155-138.670Upgrade kernelUpgrade perfUpgrade bpftool-debuginfoUpgrade python-perfUpgrade python-perf-debuginfoUpgrade kernel-livepatch-4.14.305-227.531Upgrade kernel-toolsUpgrade kernel-livepatch-5.15.79-51.138Upgrade kernel-debuginfo-common-x86_64Upgrade kernel-headers | May 20, 2026 | May 20, 2026 |
| Debian | — | Upgrade linux | Dec 31, 2025 | Dec 31, 2025 |
| Huawei Euleros 2_0_sp13 | — | Upgrade bpftoolUpgrade kernel-abi-stablelistsUpgrade kernel-toolsUpgrade kernelUpgrade python3-perfUpgrade kernel-tools-libs | Mar 10, 2026 | Mar 10, 2026 |
| Redhat_linux | — | No solution exists | Jul 17, 2026 | Dec 30, 2025 |
| Ubuntu | — | Upgrade linux-oracle-5.4Upgrade linux-intel-iotgUpgrade linux-aws-5.15Upgrade linux-oracle-5.15Upgrade linux-raspiUpgrade linux-lowlatencyUpgrade linux-gcp-5.15Upgrade linux-oracleUpgrade linux-aws-5.4Upgrade linux-nvidiaUpgrade linux-azure-fipsUpgrade linux-azure-fde-5.15Upgrade linux-gkeUpgrade linux-aws-hweUpgrade linux-gkeopUpgrade linux-riscv-5.15Upgrade linux-xilinx-zynqmpUpgrade linux-fipsUpgrade linux-azure-5.15Upgrade linux-kvmUpgrade linux-gcp-5.4Upgrade linux-azure-4.15Upgrade linux-azureUpgrade linux-lowlatency-hwe-5.15Upgrade linux-awsUpgrade linux-raspi-5.4Upgrade linux-gcp-4.15Upgrade linux-aws-fipsUpgrade linux-azure-5.4Upgrade linux-ibm-5.4Upgrade linux-realtimeUpgrade linux-hwe-5.4Upgrade linux-ibmUpgrade linux-gcp-fipsUpgrade linux-intel-iotg-5.15Upgrade linuxUpgrade linux-gcpUpgrade linux-iotUpgrade linux-hweUpgrade linux-hwe-5.15Upgrade linux-bluefield | Jan 6, 2026 | Jan 2, 2026 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | May 27, 2026 | Dec 30, 2025 |
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