CVE-2026-68297: tipc: fix u16 MTU truncation in media and bearer MTU validation
In the Linux kernel, the following vulnerability has been resolved:
tipc: fix u16 MTU truncation in media and bearer MTU validation
Both TIPCNLMEDIASET and TIPCNLBEARERSET accept user-supplied MTU values but only enforce a minimum bound, not a maximum. When a user sets the MTU to a value exceeding U16MAX (65535), it passes validation but is silently truncated when assigned to u16 fields l->mtu and l->advertisedmtu in tipclinkcreate(). Values like 65536 (0x10000) truncate to 0, causing a division by zero in tipclinksetqueuelimits() which computes TIPCMAXPUBL / (l->mtu / ITEMSIZE). 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):
tipclinksetqueuelimits net/tipc/link.c:2531 tipclinkcreate net/tipc/link.c:520 tipcnodecheckdest net/tipc/node.c:1279 tipcdiscrcv net/tipc/discover.c:252 tipcrcv net/tipc/node.c:2129 tipcudprecv net/tipc/udpmedia.c:392
Two independent paths lack the upper bound check: 1. tipcudpmtubad() -- called from tipcnlmediaset() (MEDIASET) 2. inline check in tipcnlbearerset() at bearer.c:1160 (BEARERSET)
Fix both by rejecting MTU values above U16MAX.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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Fixed in 6.6.150.1-1 - Upgrade
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Reject user-supplied MTU values above U16_MAX (65535) in both TIPC_NL_MEDIA_SET and TIPC_NL_BEARER_SET.
Linux kernel TIPC MTU validation for TIPC_NL_MEDIA_SET and TIPC_NL_BEARER_SET = maximum 65535 (U16_MAX)
Event History
Frequently Asked Questions
What is the severity of CVE-2026-68297?
CVE-2026-68297 has a risk score of 52, indicating a notable vulnerability that can be exploited.
What systems are affected by CVE-2026-68297?
CVE-2026-68297 affects the Linux kernel implementations utilizing TIPC features.
How do I fix CVE-2026-68297?
To fix CVE-2026-68297, update your Linux kernel to the latest version where the vulnerability has been patched.
What type of vulnerability is CVE-2026-68297?
CVE-2026-68297 is a truncation vulnerability related to MTU validation in the TIPC protocol.
What is TIPC in relation to CVE-2026-68297?
TIPC stands for Transparent Inter-Process Communication, which is a protocol affected by the vulnerability CVE-2026-68297.