CVE-2026-17255: CWE-787 Out-of-bounds Write

CVE-2026-17255 is an out-of-bounds write vulnerability (CWE-787) affecting IBM i operating system versions 7.3 through 7.6. The issue arises from improper validation of the prefix length field in ICMPv6 Router Advertisements, which can be exploited remotely without privileges or user interaction to cause a denial of service condition. The vulnerability is confirmed and published with a CVSS 3.1 base score of 4.3, reflecting a medium severity impact focused on availability.

Successful exploitation of this vulnerability allows a remote attacker to cause a denial of service on affected IBM i systems by triggering an out-of-bounds write through malformed ICMPv6 Router Advertisements. There is no impact to confidentiality or integrity according to the CVSS vector. No known exploits are reported in the wild.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or patch links are provided in the available data. Until a patch is available, monitoring for suspicious ICMPv6 Router Advertisements and applying network-level controls to limit exposure to untrusted IPv6 networks may help reduce risk.