Medium [CVE-2026-68297] fix u16 MTU truncation in media and bearer MTU validation
This medium-severity Red Hat Linux advisory covers CVE-2026-68297 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9.
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Summary
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.
A flaw was found in the Linux kernel's TIPC (Transparent Inter-Process Communication) module.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · medium-confidence parse· fetched 60 minutes ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · medium-confidence parse· fetched 60 minutes ago·verify at source
Mitigation
The source record does not include mitigation steps. That is not a statement that no fix exists — read the vendor advisory below for the authoritative guidance.
Official advisory · medium-confidence parse· fetched 60 minutes ago·verify at source
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