CVE-2026-68297
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.
How to fix
- Linux Linux8bfdfe0dbb36a650b7c4dec1aeae078319938a0b, dc4b577a083b361d25e118dc96d8281255ebe22c, dfdfd987f1917c84766e097a6120a1f3f1634940, f02334a9e378f7e07232b26dc3d2ab353339f040, f4013598b69457dbea350df52e52daea6faef8eb, 1b8fb5a20508bfb0db854e01214888c761b3a911, c1cda72f6acec02ebd45d913bf8527ff77336ba6, 9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Linux Linux | 901271e0403af638c224987c2a4e55cebade7e91 ≤ v < 8bfdfe0dbb36a650b7c4dec1aeae078319938a0b, 901271e0403af638c224987c2a4e55cebade7e91 ≤ v < dc4b577a083b361d25e118dc96d8281255ebe22c, 901271e0403af638c224987c2a4e55cebade7e91 ≤ v < dfdfd987f1917c84766e097a6120a1f3f1634940, 901271e0403af638c224987c2a4e55cebade7e91 ≤ v < f02334a9e378f7e07232b26dc3d2ab353339f040, 901271e0403af638c224987c2a4e55cebade7e91 ≤ v < f4013598b69457dbea350df52e52daea6faef8eb, 901271e0403af638c224987c2a4e55cebade7e91 ≤ v < 1b8fb5a20508bfb0db854e01214888c761b3a911, 901271e0403af638c224987c2a4e55cebade7e91 ≤ v < c1cda72f6acec02ebd45d913bf8527ff77336ba6, 901271e0403af638c224987c2a4e55cebade7e91 ≤ v < 9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8, 4.18 | 8bfdfe0dbb36a650b7c4dec1aeae078319938a0b, dc4b577a083b361d25e118dc96d8281255ebe22c, dfdfd987f1917c84766e097a6120a1f3f1634940, f02334a9e378f7e07232b26dc3d2ab353339f040, f4013598b69457dbea350df52e52daea6faef8eb, 1b8fb5a20508bfb0db854e01214888c761b3a911, c1cda72f6acec02ebd45d913bf8527ff77336ba6, 9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8 |
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