CVE-2026-63993 (CVSS 9.8)

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.

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CVSS v3.1 Score

9.8

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0051

Probability of exploitation

0.41%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

References

Other 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

Frequently Asked Questions

What is CVE-2026-63993? +

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. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-63993? +

CVE-2026-63993 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0051, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-63993? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

CVE-2026-63993