SB2026102387 - Observable discrepancy in Linux kernel ipv6

Description

This security bulletin contains information about 1 vulnerability.

1) Observable discrepancy (CVE-ID: CVE-2026-99076)

CWE-ID: CWE-203 - Observable discrepancy

CVSSv4: 6.3 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a remote attacker to discover the ephemeral port used by a connected UDP socket.

The vulnerability exists due to an observable discrepancy in IPv6 exception cache updates in the Linux kernel's UDP error handling when locally delivered ICMPv6 Packet Too Big or Redirect messages quote a UDP packet. A remote attacker can send crafted messages containing guessed UDP source ports and observe whether an exception is created in the cache to identify the port associated with an existing connected UDP socket.

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/8c9b310c958be33ba8fb9d0e6b77811d013e10c0
• https://git.kernel.org/stable/c/ac76cab50e899a7346408b8d3c3a4192c2eefb9f