{"id":"CVE-2026-89563","title":"ip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()\n\nip6_tnl_xmit() may need to expand headroom before it can push the\nouter IPv6 and optional encap headers. It currently …","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","cwe":["CWE-1341"],"vendor":"Linux","product":"Linux","affected":["Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < 6e8eff8ed13b14708bc39f170144eacde494aac6","Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < dc1a319a4815c074914e2812e0e9cd0164ca682b","Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < 629d5557e635cdbc109a14ed913ba5a540e3f79a","Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < defa0adeff132cc90ed66915b9a104d9393e1e54","Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < 37df5bc6b5ccad88c2faa0f5466f150178882b74","Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < b36dfd6e8cff00cea81c11cc0af88d1564763461","Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < 8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52","Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < 87f21b59ddc618eff9670c174842964ad65fdade","Linux 4.7"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T19:24:12.096672Z"},"published":"2026-09-11","updated":"2026-10-19","sourceUpdated":"2026-10-19T08:48:56.784Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89563","references":[{"url":"https://git.kernel.org/stable/c/6e8eff8ed13b14708bc39f170144eacde494aac6"},{"url":"https://git.kernel.org/stable/c/dc1a319a4815c074914e2812e0e9cd0164ca682b"},{"url":"https://git.kernel.org/stable/c/629d5557e635cdbc109a14ed913ba5a540e3f79a"},{"url":"https://git.kernel.org/stable/c/defa0adeff132cc90ed66915b9a104d9393e1e54"},{"url":"https://git.kernel.org/stable/c/37df5bc6b5ccad88c2faa0f5466f150178882b74"},{"url":"https://git.kernel.org/stable/c/b36dfd6e8cff00cea81c11cc0af88d1564763461"},{"url":"https://git.kernel.org/stable/c/8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52"},{"url":"https://git.kernel.org/stable/c/87f21b59ddc618eff9670c174842964ad65fdade"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89563.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89563"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532305"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89563"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89563"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89563.mbox"}],"tags":["cve.org","csaf","vex","red-hat"],"epss":0.00139,"epssPercentile":0.03214,"scores":{"cna":7.8,"vendor":7},"ingestedAt":"2026-09-14T15:23:07.451Z","slug":"CVE-2026-89563","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nip6_tunnel: use skb_cow_head() in ip6_tnl_xmit()\n\nip6_tnl_xmit() may need to expand headroom before it can push the\nouter IPv6 and optional encap headers. It currently does that with\nskb_realloc_headroom(), copies skb->sk ownership, consumes the original\nskb, and then continues processing with the replacement skb kept only in\nits local variable.\n\nThat is safe only if the helper cannot fail afterwards. But this helper\nstill has post-reallocation error exits. collect_md tunnels reject\nnon-NONE encap after the replacement, and ip6_tnl_encap() can also fail\nlater. In those cases the helper returns an error to its callers while\nthe caller still only has the original skb pointer.\n\nBoth ip6_tnl_start_xmit() and the IPv6 GRE paths free the caller skb on\nerror, so they can end up freeing an skb that ip6_tnl_xmit() already\nconsumed.\n\nUse skb_cow_head() instead. It provides the required headroom and\nwritability without privately replacing the caller-owned skb, so later\nerror returns cannot leave callers with a stale pointer.\n\nThe Ethernet users, ip6gretap and ip6erspan, clear IFF_TX_SKB_SHARING\nand already call skb_cow_head() before entering ip6_tnl_xmit(). They do\nnot rely on the removed skb_shared() reallocation. This also makes the\nIPv6 tunnel path consistent with ip_tunnel_xmit().\n\n## Affected\n\n- `Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < 6e8eff8ed13b14708bc39f170144eacde494aac6`\n- `Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < dc1a319a4815c074914e2812e0e9cd0164ca682b`\n- `Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < 629d5557e635cdbc109a14ed913ba5a540e3f79a`\n- `Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < defa0adeff132cc90ed66915b9a104d9393e1e54`\n- `Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < 37df5bc6b5ccad88c2faa0f5466f150178882b74`\n- `Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < b36dfd6e8cff00cea81c11cc0af88d1564763461`\n- `Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < 8fc56ca49fc0ee1725b55c67bb43ab0dd01f3f52`\n- `Linux >= 058214a4d1dfefed9f01a277fadd3590acb5f990 < 87f21b59ddc618eff9670c174842964ad65fdade`\n- `Linux 4.7`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4, Red Hat Enterprise Linux 6 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89563.json)","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[{"seq":223281,"id":"CVE-2026-89563","ts":1792180041434,"field":"cvss","old":"7","new":"7.8"},{"seq":208102,"id":"CVE-2026-89563","ts":1789922708983,"field":"cvss","old":"7.8","new":"7"},{"seq":197920,"id":"CVE-2026-89563","ts":1789384320955,"field":"cvss","old":"4.4","new":"7.8"},{"seq":197919,"id":"CVE-2026-89563","ts":1789384320955,"field":"severity","old":"medium","new":"high"},{"seq":183463,"id":"CVE-2026-89563","ts":1789356675469,"field":"cvss","old":"7.8","new":"4.4"},{"seq":183462,"id":"CVE-2026-89563","ts":1789356675469,"field":"severity","old":"high","new":"medium"},{"seq":153378,"id":"CVE-2026-89563","ts":1789285350274,"field":"cvss","old":null,"new":"7.8"},{"seq":153377,"id":"CVE-2026-89563","ts":1789285350274,"field":"severity","old":"none","new":"high"},{"seq":147400,"id":"CVE-2026-89563","ts":1789270210762,"field":"cvss","old":null,"new":"4.4"},{"seq":147399,"id":"CVE-2026-89563","ts":1789270210762,"field":"severity","old":"none","new":"medium"},{"seq":109150,"id":"CVE-2026-89563","ts":1789183730509,"field":"cvss","old":null,"new":"4.4"},{"seq":109149,"id":"CVE-2026-89563","ts":1789183730509,"field":"severity","old":"none","new":"medium"}]}