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Fencer Intel
medium 5.5

CVE-2025-71098 json

ip6_gre: make ip6gre_header() robust

published 9mo ago modified 21d ago also EUVD-2026-2221

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

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

Patch / fix

  • Linux Linux 5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.64, 6.18.4, 6.19
  • linux Debian 12 6.1.162-1
  • linux Debian 13 6.12.69-1
  • linux Debian 14 6.18.5-1

debian advisories DEBIAN-CVE-2025-71098

  • linux Ubuntu 22.04 LTS 5.15.0-173.183
  • linux Ubuntu 24.04 LTS 6.8.0-110.110
  • linux Ubuntu 25.10 6.17.0-22.22
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1103.110
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1052.55
  • linux-aws Ubuntu 25.10 6.17.0-1012.12
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1103.112
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1054.57

ubuntu advisories UBUNTU-CVE-2025-71098

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-40.1
  • kernel-source-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-40.1
  • kernel-rt Linux Micro 6.2 6.12.0-160000.26.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.26.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.26.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.26.1
  • kernel-default-base SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.26.1.160000.2.7
  • kernel-syms SLES 16.0, Linux Micro Extras 6.2, SLES for SAP applications 16.0 6.12.0-160000.26.1

suse advisories SUSE-SU-2026:20845-1SUSE-SU-2026:20876-1SUSE-SU-2026:20555-1SUSE-SU-2026:20599-1SUSE-SU-2026:20615-1SUSE-SU-2026:20570-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.26.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.26.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.26.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.26.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.26.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.26.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.26.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.26.1

opensuse advisories openSUSE-SU-2026:20287-1

Is CVE-2025-71098 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-71098 updated cvss 6.2

kernel: ip6_gre: make ip6gre_header() robust

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    affected: no fix available
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-26-295-11 updated cvss 6.2

Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.7 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.7 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.7
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

cisa ICSA-26-209-04 updated cvss 6.2

Siemens SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.6 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.6 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.6
    affected: mitigation, no fix available

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
4mo ago

Exploit prediction

0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux
  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP

Classification

Weakness
  • CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
  • CWE-476 NULL Pointer Dereference
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.