--- id: CVE-2026-63992 title: |- In the Linux kernel, the following vulnerability has been resolved: tunnels: do not assume transport header in iptunnel_pmtud_check_icmp() In some cases, iptunnel_pmtud_check_icmp() can be called while skb transport header is not set. … summary: |- In the Linux kernel, the following vulnerability has been resolved: tunnels: do not assume transport header in iptunnel_pmtud_check_icmp() In some cases, iptunnel_pmtud_check_icmp() can be called while skb transport header is not set. … severity: critical cvss: 9.1 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H' cwe: - CWE-125 - CWE-805 vendor: linux product: linux_kernel affected: - 'linux_kernel >= 5.9, < 5.10.259' - 'linux_kernel >= 5.11, < 5.15.210' - 'linux_kernel >= 5.16, < 6.1.176' - 'linux_kernel >= 6.2, < 6.6.143' - 'linux_kernel >= 6.7, < 6.12.93' - 'linux_kernel >= 6.13, < 6.18.35' - 'linux_kernel >= 6.19, < 7.0.12' - linux_kernel = 7.1 patched: - linux_kernel 7.0.12 published: '2026-07-19' updated: '2026-10-07' sourceUpdated: '2026-10-07T20:29:43.487' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63992' references: - url: 'https://git.kernel.org/stable/c/43368636c663cff6e59dde93cf4b8e43ac28eb93' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/509323077ef79a26ba0c60bb556e45c12c398b2d' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/5a92cb45e34749865d03daf8d3500f77b5f6644c' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/7f4f7efe7f30edd29c4988de01728bf2398217e4' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/a096b6e34f602950af9a2b0856cd93a5f4c276d7' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/c7b7ec3e69e673c0d6b57f74d21da50c485c598e' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/cb549df9ce4ee15c9d5b19ddab12cf2128e4313c' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/e917d0c69f01af2bb4fbea2b66d560a53b3ac7ec' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63992.json - url: 'https://access.redhat.com/security/cve/CVE-2026-63992' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2502431' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-63992' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63992' - url: >- https://lore.kernel.org/linux-cve-announce/2026071904-CVE-2026-63992-2846@gregkh/T - url: 'https://access.redhat.com/errata/RHSA-2026:76738' - url: 'https://access.redhat.com/errata/RHSA-2026:76739' - url: 'https://access.redhat.com/errata/RHSA-2026:75747' - url: 'https://access.redhat.com/errata/RHSA-2026:75746' tags: - nvd - cve.org - csaf - vex - red-hat - score-dispute epss: 0.00514 epssPercentile: 0.43612 ingestedAt: '2026-10-07T20:46:46.957Z' ssvc: exploitation: none automatable: 'yes' technicalImpact: partial timestamp: '2026-10-16T15:34:46.388136Z' scores: nvd: 9.1 vendor: 7 --- ## Overview In the Linux kernel, the following vulnerability has been resolved: tunnels: do not assume transport header in iptunnel_pmtud_check_icmp() In some cases, iptunnel_pmtud_check_icmp() can be called while skb transport header is not set. This triggers an out-of-bound access, because (typeof(skb->transport_header))~0U is 65535. Access the icmp header based on IPv4 network header, after making sure icmp->type is present in skb linear part. Note that iptunnel_pmtud_check_icmpv6()) is fine. ## Affected - `linux_kernel >= 5.9, < 5.10.259` - `linux_kernel >= 5.11, < 5.15.210` - `linux_kernel >= 5.16, < 6.1.176` - `linux_kernel >= 6.2, < 6.6.143` - `linux_kernel >= 6.7, < 6.12.93` - `linux_kernel >= 6.13, < 6.18.35` - `linux_kernel >= 6.19, < 7.0.12` - `linux_kernel = 7.1` ## Remediation Upgrade past the affected range: - `linux_kernel 7.0.12` ## Vendor advisories - **RHSA-2026:76738** · Red Hat · fixed in: 10Base-SMTV, Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10), Red Hat Enterprise Linux Hidden (v. 10), Red Hat Enterprise Linux Real Time for NFV (v. 10), … · released 2026-10-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:76738) - **RHSA-2026:76739** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Real Time for NFV (v. 9), Red Hat Enterprise Linux Real Time (v. 9) · released 2026-10-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:76739) - **RHSA-2026:75747** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8), Red Hat Enterprise Linux CRB (v. 8) · released 2026-10-05 · [advisory](https://access.redhat.com/errata/RHSA-2026:75747) - **RHSA-2026:75746** · Red Hat · fixed in: Red Hat Enterprise Linux NFV (v. 8), Red Hat Enterprise Linux RT (v. 8) · released 2026-10-05 · [advisory](https://access.redhat.com/errata/RHSA-2026:75746) - **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 9 · updated 2026-10-26 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63992.json)