CVE-2026-99077 Linux Kernel - Information Disclosure

Linux kernel contains a side-channel vulnerability in IPv4 UDP handling caused by conditional creation of FIB nexthop exceptions only after socket matching, letting off-path attackers discover ephemeral UDP ports, exploit requires sending crafted ICMP packets.

CVSS base score 7.4 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.21% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Information Disclosure
Impact
Information Disclosure
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Published
23 October 2026
Updated
25 October 2026

Vendor fix

Update to the latest Linux kernel version containing the fix for FNHE creation before socket matching.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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