CVE-2026-89563 json
ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()
published 2026-09-11 58 d ago modified 2026-10-19 21 d ago also EUVD-2026-76474
- cvss
- 7.8
- version 3.1, CNA
- 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_tunnel: use skb_cow_head() in ip6_tnl_xmit()
ip6_tnl_xmit() may need to expand headroom before it can push the outer IPv6 and optional encap headers. It currently does that with skb_realloc_headroom(), copies skb->sk ownership, consumes the original skb, and then continues processing with the replacement skb kept only in its local variable.
That is safe only if the helper cannot fail afterwards. But this helper still has post-reallocation error exits. collect_md tunnels reject non-NONE encap after the replacement, and ip6_tnl_encap() can also fail later. In those cases the helper returns an error to its callers while the caller still only has the original skb pointer.
Both ip6_tnl_start_xmit() and the IPv6 GRE paths free the caller skb on error, so they can end up freeing an skb that ip6_tnl_xmit() already consumed.
Use skb_cow_head() instead. It provides the required headroom and writability without privately replacing the caller-owned skb, so later error returns cannot leave callers with a stale pointer.
The Ethernet users, ip6gretap and ip6erspan, clear IFF_TX_SKB_SHARING and already call skb_cow_head() before entering ip6_tnl_xmit(). They do not rely on the removed skb_shared() reallocation. This also makes the IPv6 tunnel path consistent with ip_tunnel_xmit().
Patch / fix
- Linux Linux 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, 6.18.50, 7.2.4, 7.3
- linux Debian 12 6.1.190-1
- linux Debian 13 6.12.111-1
- linux Debian 14 7.2.6-1
- linux-6.12 Debian 12 6.12.111-1~deb12u1
debian advisories DEBIAN-CVE-2026-89563
- linux Ubuntu 22.04 LTS 5.15.0-202.212
- linux Ubuntu 26.04 LTS 7.0.0-42.42
- linux-aws Ubuntu 22.04 LTS 5.15.0-1119.126
- linux-aws Ubuntu 26.04 LTS 7.0.0-1016.17
- linux-gcp Ubuntu 22.04 LTS 5.15.0-1120.130
- linux-gcp Ubuntu 26.04 LTS 7.0.0-1016.18
- linux-gke Ubuntu 22.04 LTS 5.15.0-1115.121
- linux-ibm Ubuntu 22.04 LTS 5.15.0-1113.117
ubuntu advisories UBUNTU-CVE-2026-89563
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-source openSUSE Tumbleweed 7.2.7-1.1
opensuse advisories openSUSE-SU-2026:11880-1
- kernel Azure Linux 3.0 6.6.157.1-1
azure linux advisories AZL-100262
Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT
- git.kernel.org/stable/c/6e8eff8ed13b14708bc39f170144eacde494aac6 commit
- git.kernel.org/stable/c/dc1a319a4815c074914e2812e0e9cd0164ca682b commit
- git.kernel.org/stable/c/629d5557e635cdbc109a14ed913ba5a540e3f79a commit
- git.kernel.org/stable/c/defa0adeff132cc90ed66915b9a104d9393e1e54 commit
- git.kernel.org/stable/c/37df5bc6b5ccad88c2faa0f5466f150178882b74 commit
- git.kernel.org/stable/c/b36dfd6e8cff00cea81c11cc0af88d1564763461 commit
- git.kernel.org/stable/c/8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52 commit
- git.kernel.org/stable/c/87f21b59ddc618eff9670c174842964ad65fdade commit
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-2026-89563 updated cvss 7.8
kernel: ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()
-
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 kernelaffected: workaround, no fix available
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Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 morenot 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 SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 23 d ago
Exploit prediction
0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
Affected products
- Linux Linux
Classification
- Technology feeds
References
- git.kernel.org /stable/c/6e8eff8ed13b14708bc39f170144eacde494aac6
- git.kernel.org /stable/c/dc1a319a4815c074914e2812e0e9cd0164ca682b
- git.kernel.org /stable/c/629d5557e635cdbc109a14ed913ba5a540e3f79a
- git.kernel.org /stable/c/defa0adeff132cc90ed66915b9a104d9393e1e54
- git.kernel.org /stable/c/37df5bc6b5ccad88c2faa0f5466f150178882b74
- git.kernel.org /stable/c/b36dfd6e8cff00cea81c11cc0af88d1564763461
- git.kernel.org /stable/c/8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52
- git.kernel.org /stable/c/87f21b59ddc618eff9670c174842964ad65fdade
Sources
- CVE List CVE-2026-89563
- NVD CVE-2026-89563
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