--- id: CVE-2026-63994 title: >- In the Linux kernel, the following vulnerability has been resolved: tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]() Sashiko found that iptunnel_pmtud_build_icmp() and iptunnel_pmtud_build_icmpv6() were … summary: >- In the Linux kernel, the following vulnerability has been resolved: tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]() Sashiko found that iptunnel_pmtud_build_icmp() and iptunnel_pmtud_build_icmpv6() were … severity: critical cvss: 9.8 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H' cwe: - CWE-416 - CWE-825 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: '2026-10-07T20:28:32.877' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63994' references: - url: 'https://git.kernel.org/stable/c/50750d86a2e5266aba0c295483b3397843198b11' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/6dff77899b9e9fe5d854abda3a98ad04e7229ef7' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/7254aef4d1a7e18e887af9010e2f2dc34806789b' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/76cd9398a0470257ab765bdf5f358a2af2e17934' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/95b6d772bfe788331d9742d73eaa12e113b2adc4' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/b4bc94353050b1fa7b702bd4c6600710dd926cff' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/bf8b3f34c37c162357138e7c0942723b8b94fed1' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/f3f204541f280a6ecb04503a0d6794d93990ca43' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63994.json - url: 'https://access.redhat.com/security/cve/CVE-2026-63994' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2502444' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-63994' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63994' - url: >- https://lore.kernel.org/linux-cve-announce/2026071905-CVE-2026-63994-97bf@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: 0.43608 ingestedAt: '2026-10-07T20:46:46.957Z' ssvc: exploitation: none automatable: 'yes' technicalImpact: total timestamp: '2026-10-16T15:34:51.504885Z' scores: nvd: 9.8 vendor: 7 --- ## Overview In the Linux kernel, the following vulnerability has been resolved: tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]() Sashiko found that iptunnel_pmtud_build_icmp() and iptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr() before an skb_cow() call which can reallocate skb->head. Fix this possible UAF by initializing the local variables after the skb_cow() call. Remove skb_reset_network_header() calls which were not needed. ## 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** · Important · affected: Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 6 · no fix planned: Red Hat Enterprise Linux 9 · updated 2026-10-26 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63994.json)