CVE-2026-68297 tipc: fix u16 MTU truncation in media and bearer MTU validation
An integer overflow in Linux kernel TIPC MTU validation allows unprivileged users to trigger a division by zero, causing a system crash.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-68297?
CVE-2026-68297 is a high-severity vulnerability in Linux, published on 10 Aug 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:
tipc: fix u16 MTU truncation in media and bearer MTU validation
Both TIPC_NL_MEDIA_SET and TIPC_NL_BEARER_SET accept user-supplied MTU values but only enforce a minimum bound, not a maximum. When a user sets the MTU to a value exceeding U16_MAX (65535), it passes validation but is silently truncated when assigned to u16 fields l->mtu and l->advertised_mtu in tipc_link_create(). Values like 65536 (0x10000) truncate to 0, causing a division by zero in tipc_link_set_queue_limits() which computes TIPC_MAX_PUBL / (l->mtu / ITEM_SIZE). Other overflowing values (e.g. 65537-131071) produce small incorrect MTU values, resulting in link malfunction behaviors.
Crash stack (triggered as unprivileged user via user namespace):
tipc_link_set_queue_limits net/tipc/link.c:2531 tipc_link_create net/tipc/link.c:520 tipc_node_check_dest net/tipc/node.c:1279 tipc_disc_rcv net/tipc/discover.c:252 tipc_rcv net/tipc/node.c:2129 tipc_udp_recv net/tipc/udp_media.c:392
Two independent paths lack the upper bound check: 1. tipc_udp_mtu_bad() -- called from __tipc_nl_media_set() (MEDIA_SET) 2. inline check in __tipc_nl_bearer_set() at bearer.c:1160 (BEARER_SET)
Fix both by rejecting MTU values above U16_MAX.
Weakness: CWE-190
Which versions are affected by CVE-2026-68297?
How do I fix CVE-2026-68297?
Apply the vendor's patch.
Is CVE-2026-68297 being exploited?
There is no known exploitation of CVE-2026-68297 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-68297, DEBIAN-CVE-2026-68297, GHSA-prmr-9j2x-c47h, UBUNTU-CVE-2026-68297.