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Vulnerability · Published Jul 19, 2026 · Assigned by Linux

CVE-2026-63993vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()

Critical 9.8

In plain English

A critical-severity use-after-free in Linux from Linux. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.5%top 56.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

In the Linux kernel, the following vulnerability has been resolved: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu() skb_tunnel_check_pmtu() can change skb->head. Reusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF. Use instead ip_hdr(skb) as done in drivers/net/bareudp.c and drivers/net/geneve.c. Found by Sashiko.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12linux6.1.176-1DEBIAN-CVE-2026-63993
Debian:13linux6.12.94-1DEBIAN-CVE-2026-63993
Debian:14linux7.0.12-1DEBIAN-CVE-2026-63993
Rocky Linux:10kernel0:6.12.0-211.52.1.el10_2RLSA-2026:64775
Ubuntu:22.04:LTSlinux5.15.0-194.204USN-8818-4
Ubuntu:22.04:LTSlinux5.15.0-194.204UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux6.8.0-142.142USN-8817-1
Ubuntu:24.04:LTSlinux6.8.0-142.142UBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux7.0.0-28.28UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-allwinner-5.19no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-aws5.15.0-1116.123UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-aws5.15.0-1116.123USN-8818-1
Ubuntu:24.04:LTSlinux-aws6.8.0-1065.68USN-8817-3
Ubuntu:24.04:LTSlinux-aws6.8.0-1065.68UBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-aws7.0.0-1009.9UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-aws-5.19no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-aws-6.14no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-aws-6.17no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-aws-6.2no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-aws-6.5no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-aws-6.86.8.0-1065.68~22.04.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-aws-6.86.8.0-1065.68~22.04.1USN-8817-3
Ubuntu:22.04:LTSlinux-azure5.15.0-1122.131UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure5.15.0-1122.131USN-8818-1
Ubuntu:24.04:LTSlinux-azure6.8.0-1068.76USN-8817-1
Ubuntu:24.04:LTSlinux-azure6.8.0-1068.76UBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-azure7.0.0-1010.10UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure-5.19no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-azure-6.11no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-azure-6.14no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-azure-6.17no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure-6.2no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure-6.5no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure-6.86.8.0-1068.76~22.04.1USN-8817-1
Ubuntu:22.04:LTSlinux-azure-6.86.8.0-1068.76~22.04.1UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-azure-7.07.0.0-1014.14~24.04.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure-fde5.15.0-1121.130UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure-fde5.15.0-1121.130USN-8818-1
Ubuntu:24.04:LTSlinux-azure-fde6.8.0-1066.73USN-8817-1
Ubuntu:24.04:LTSlinux-azure-fde6.8.0-1066.73UBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-azure-fde7.0.0-1009.9UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure-fde-5.19no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-azure-fde-6.14no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-azure-fde-6.17no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure-fde-6.2no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure-fde-6.86.8.0-1066.73~22.04.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-azure-fde-6.86.8.0-1066.73~22.04.1USN-8817-1
Ubuntu:24.04:LTSlinux-azure-fde-7.07.0.0-1013.13~24.04.1UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-azure-nvidiano fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-azure-nvidia-6.14no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-gcp5.15.0-1117.127UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-gcp5.15.0-1117.127USN-8818-1
Ubuntu:24.04:LTSlinux-gcp6.8.0-1069.77UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-gcp6.8.0-1069.77USN-8817-1
Ubuntu:26.04:LTSlinux-gcp7.0.0-1008.8UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-gcp-5.19no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-gcp-6.11no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-gcp-6.14no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-gcp-6.17no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-gcp-6.2no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-gcp-6.5no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-gcp-6.86.8.0-1069.77~22.04.1USN-8817-1
Ubuntu:22.04:LTSlinux-gcp-6.86.8.0-1069.77~22.04.1UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-gcp-7.07.0.0-1011.11~24.04.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-gke5.15.0-1112.118USN-8818-1
Ubuntu:22.04:LTSlinux-gke5.15.0-1112.118UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-gke6.8.0-1064.72UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-gke6.8.0-1064.72USN-8817-1
Ubuntu:26.04:LTSlinux-gke7.0.0-1003.4UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-gkeop5.15.0-1099.107USN-8818-1
Ubuntu:22.04:LTSlinux-gkeop5.15.0-1099.107UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-gkeop6.8.0-1050.54UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-gkeop6.8.0-1050.54USN-8817-1
Ubuntu:22.04:LTSlinux-hwe-5.19no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-hwe-6.11no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-hwe-6.14no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-hwe-6.17no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-hwe-6.2no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-hwe-6.5no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-hwe-6.8no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-hwe-7.07.0.0-28.28~24.04.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-ibm5.15.0-1110.114UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-ibm5.15.0-1110.114USN-8818-1
Ubuntu:24.04:LTSlinux-ibm6.8.0-1065.66USN-8817-1
Ubuntu:24.04:LTSlinux-ibm6.8.0-1065.66UBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-ibm7.0.0-1010.10UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-ibm-6.86.8.0-1066.67~22.04.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-intel-iot-realtimeno fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-intel-iotg5.15.0-1111.117USN-8818-1
Ubuntu:22.04:LTSlinux-intel-iotg5.15.0-1111.117UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-kvm5.15.0-1108.113UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-kvm5.15.0-1108.113USN-8818-1
Ubuntu:22.04:LTSlinux-lowlatency5.15.0-194.204USN-8818-1
Ubuntu:22.04:LTSlinux-lowlatency5.15.0-194.204UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-lowlatency6.8.0-142.142.1USN-8817-1
Ubuntu:24.04:LTSlinux-lowlatency6.8.0-142.142.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-lowlatency-hwe-5.19no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-lowlatency-hwe-6.11no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.2no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.5no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.86.8.0-142.142.1~22.04.1USN-8817-1
Ubuntu:22.04:LTSlinux-lowlatency-hwe-6.86.8.0-142.142.1~22.04.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-nvidia5.15.0-1111.112UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-nvidia5.15.0-1111.112USN-8818-4
Ubuntu:24.04:LTSlinux-nvidia6.8.0-1063.66USN-8842-1
Ubuntu:24.04:LTSlinux-nvidia6.8.0-1063.66UBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-nvidia7.0.0-1016.16UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-nvidia-6.11no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-nvidia-6.17no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-nvidia-6.2no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-nvidia-6.5no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-nvidia-6.86.8.0-1063.66~22.04.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-nvidia-6.86.8.0-1063.66~22.04.1USN-8842-1
Ubuntu:24.04:LTSlinux-nvidia-7.07.0.0-1016.16~24.04.1UBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-nvidia-bos7.0.0-2016.16UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-nvidia-lowlatency6.8.0-1063.66.1USN-8842-1
Ubuntu:24.04:LTSlinux-nvidia-lowlatency6.8.0-1063.66.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-nvidia-tegra5.15.0-1068.70UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-nvidia-tegra5.15.0-1068.70USN-8818-5
Ubuntu:24.04:LTSlinux-nvidia-tegra6.8.0-1035.38UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-nvidia-tegra-igx5.15.0-1057.57USN-8818-5
Ubuntu:22.04:LTSlinux-nvidia-tegra-igx5.15.0-1057.57UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-oem-5.17no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-oem-6.0no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-oem-6.1no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-oem-6.11no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-oem-6.14no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-oem-6.17no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-oem-6.5no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-oem-6.8no fix listedUBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-oem-7.07.0.0-1009.9UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-oracle5.15.0-1113.119UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-oracle5.15.0-1113.119USN-8818-1
Ubuntu:24.04:LTSlinux-oracle6.8.0-1062.65USN-8817-1
Ubuntu:24.04:LTSlinux-oracle6.8.0-1062.65UBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-oracle7.0.0-1008.8UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-oracle-6.14no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-oracle-6.17no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-oracle-6.5no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-oracle-6.86.8.0-1062.65~22.04.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-oracle-6.86.8.0-1062.65~22.04.1USN-8817-1
Ubuntu:24.04:LTSlinux-oracle-7.07.0.0-1011.11~24.04.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-raspi5.15.0-1110.113USN-8871-1
Ubuntu:22.04:LTSlinux-raspi5.15.0-1110.113UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-raspi6.8.0-1065.69USN-8817-1
Ubuntu:24.04:LTSlinux-raspi6.8.0-1065.69UBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-raspi7.0.0-1015.15UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-raspi-realtimeno fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-realtimeno fix listedUBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-realtime7.0.0-28.28.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-riscvno fix listedUBUNTU-CVE-2026-63993
Ubuntu:26.04:LTSlinux-riscv7.0.0-28.28.1UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-riscv-5.19no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-riscv-6.14no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-riscv-6.17no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-riscv-6.5no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-riscv-6.86.8.0-142.142~22.04.1UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-riscv-7.07.0.0-28.28.1~24.04.3UBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-starfive-5.19no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-starfive-6.2no fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-starfive-6.5no fix listedUBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-vmware6.8.0-1008.8UBUNTU-CVE-2026-63993
Ubuntu:24.04:LTSlinux-xilinxno fix listedUBUNTU-CVE-2026-63993
Ubuntu:22.04:LTSlinux-xilinx-zynqmp5.15.0-1079.83USN-8818-1
Ubuntu:22.04:LTSlinux-xilinx-zynqmp5.15.0-1079.83UBUNTU-CVE-2026-63993

Affected products (as reported)

VendorProductVersions
Linux Linux 4cb47a8644cc9eb8ec81190a50e79e6530d0297f – before 6b8bfce9d2f774d2c2243e0248e03efb99bba6c04cb47a8644cc9eb8ec81190a50e79e6530d0297f – before 9257f56ac47ef1976bcd056cf986a9988eeec67a4cb47a8644cc9eb8ec81190a50e79e6530d0297f – before 8d435d68d71fb875876b722f4136caf74f2f48bd4cb47a8644cc9eb8ec81190a50e79e6530d0297f – before dc3bfa050f873371e745bdf478b1f5b738e5733d4cb47a8644cc9eb8ec81190a50e79e6530d0297f – before 609e63312c29aad18026a1d3222e123d4b6b0feb4cb47a8644cc9eb8ec81190a50e79e6530d0297f – before 5303925e360527243b46a440a04667826bbc72b74cb47a8644cc9eb8ec81190a50e79e6530d0297f – before a493efd4336cf19122ae0e4cbb3d31b32d70deea4cb47a8644cc9eb8ec81190a50e79e6530d0297f – before 7d9ef0cb271555d8cf39fefe6c981e1493b25ecf
Linux Linux 5.9

Weakness: CWE-416 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References