CVE-2026-98493net: ipconfig: bound DHCP option construction

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/e0a221cec0e0ee437680ae0314a4b166509442c5
• https://git.kernel.org/stable/c/ca811550b9fa87e02845b4a332d194c2304d933f
• https://git.kernel.org/stable/c/d8016c82acdd7eaa462e1f38a962b15d8c6a650b
• https://git.kernel.org/stable/c/38a6a118260ebfc82d0c653194d616bdfbd236ac
• https://git.kernel.org/stable/c/abcba6f080c63e403037ecdffde43170d242376a
• https://git.kernel.org/stable/c/24e79508b237dd2a69bc6fb6ac5cf7f126178307
• https://git.kernel.org/stable/c/cbaad2922bd5d4d303055ae9afecc8999e6b40c9
• https://git.kernel.org/stable/c/e47a1958e12abc3a17b5231a4f21c8f1bf662e08