What’s Vulnerable › Vulnerabilities

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

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-19 · updated 2026-10-19
• Weakness: CWE-416

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 products

• Linux kernel: from 5.9 before 5.10.259; from 5.11 before 5.15.210; from 5.16 before 6.1.176; from 6.2 before 6.6.143; from 6.7 before 6.12.93; from 6.13 before 6.18.35 — fixed in 5.10.259, 5.15.210, 6.1.176, 6.12.93, 6.18.35, 6.6.143

How to fix

Upgrade to a fixed version: Linux kernel 5.10.259, 5.15.210, 6.1.176, 6.12.93. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/5303925e360527243b46a440a04667826bbc72b7
• https://git.kernel.org/stable/c/609e63312c29aad18026a1d3222e123d4b6b0feb
• https://git.kernel.org/stable/c/6b8bfce9d2f774d2c2243e0248e03efb99bba6c0
• https://git.kernel.org/stable/c/7d9ef0cb271555d8cf39fefe6c981e1493b25ecf
• https://git.kernel.org/stable/c/8d435d68d71fb875876b722f4136caf74f2f48bd
• https://git.kernel.org/stable/c/9257f56ac47ef1976bcd056cf986a9988eeec67a
• https://git.kernel.org/stable/c/a493efd4336cf19122ae0e4cbb3d31b32d70deea
• https://git.kernel.org/stable/c/dc3bfa050f873371e745bdf478b1f5b738e5733d

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