CVE-2026-98493

In the Linux kernel, the following vulnerability has been resolved:

net: ipconfig: bound DHCP option construction

ic dhcp init options() appends the hostname (option 12), vendor-class (option 60) and client-ID (option 61) options into the fixed 312-byte bootp pkt.exten[] buffer. Only the client-ID branch checked the remaining space; the hostname and vendor-class writes were unbounded.

A 64-byte hostname together with the maximum 252-byte dhcpclass= identifier needs 18 + (2 + 64) + (2 + 252) = 338 of the 312 available bytes even before the terminating END marker, so the vendor-class memcpy runs past the end of exten[]. With CONFIG FORTIFY SOURCE this is reported as a field-spanning write and, when the kernel is booted with panic on warn=1, aborts boot with a panic.

Route the optional options through a common helper that makes sure the option, its 2-byte header and the END marker all fit and drops an option that would not. Configurations with short options keep sending exactly the same bytes as before.