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CVE-2026-63993

CRITICALCVSS 9.8/10EPSS 0.51%

Last modified

CVE-2026-63993 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 0.51% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
9.8/10

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

EPSS Probability
0.51%

40.9th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
LinuxLinux>= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 6b8bfce9d2f774d2c2243e0248e03efb99bba6c0; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 9257f56ac47ef1976bcd056cf986a9988eeec67a; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 8d435d68d71fb875876b722f4136caf74f2f48bd; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < dc3bfa050f873371e745bdf478b1f5b738e5733d; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 609e63312c29aad18026a1d3222e123d4b6b0feb; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 5303925e360527243b46a440a04667826bbc72b7; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < a493efd4336cf19122ae0e4cbb3d31b32d70deea; >= 4cb47a8644cc9eb8ec81190a50e79e6530d0297f, < 7d9ef0cb271555d8cf39fefe6c981e1493b25ecf
LinuxLinux5.9

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

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.
How severe is CVE-2026-63993?
CVE-2026-63993 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.51% probability of exploitation in the next 30 days.
How do I fix CVE-2026-63993?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST