CVE-2026-98493 net: ipconfig: bound DHCP option construction
A buffer overflow in the Linux kernel DHCP option construction allows a local attacker to cause a system panic via crafted hostname and vendor-class options.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98493?
CVE-2026-98493 is a memory corruption vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
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.
Which versions are affected by CVE-2026-98493?
How do I fix CVE-2026-98493?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-98493 being exploited?
There is no known exploitation of CVE-2026-98493 in the wild and no public exploit code.
Sources
Also known as AZL-108671, BELL-CVE-2026-98493, DEBIAN-CVE-2026-98493, GHSA-x4fq-3fw2-872x, UBUNTU-CVE-2026-98493.