GHSA-PRMR-9J2X-C47H
Vulnerability from github – Published: 2026-08-10 15:33 – Updated: 2026-08-19 18:32In 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.
{
"affected": [],
"aliases": [
"CVE-2026-68297"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-10T13:20:19Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix u16 MTU truncation in media and bearer MTU validation\n\nBoth TIPC_NL_MEDIA_SET and TIPC_NL_BEARER_SET accept user-supplied\nMTU values but only enforce a minimum bound, not a maximum. When a user\nsets the MTU to a value exceeding U16_MAX (65535), it passes validation\nbut is silently truncated when assigned to u16 fields l-\u003emtu and\nl-\u003eadvertised_mtu in tipc_link_create(). Values like 65536 (0x10000)\ntruncate to 0, causing a division by zero in tipc_link_set_queue_limits()\nwhich computes TIPC_MAX_PUBL / (l-\u003emtu / ITEM_SIZE). Other overflowing\nvalues (e.g. 65537-131071) produce small incorrect MTU values, resulting\nin link malfunction behaviors.\n\nCrash stack (triggered as unprivileged user via user namespace):\n\n tipc_link_set_queue_limits net/tipc/link.c:2531\n tipc_link_create net/tipc/link.c:520\n tipc_node_check_dest net/tipc/node.c:1279\n tipc_disc_rcv net/tipc/discover.c:252\n tipc_rcv net/tipc/node.c:2129\n tipc_udp_recv net/tipc/udp_media.c:392\n\nTwo independent paths lack the upper bound check:\n1. tipc_udp_mtu_bad() -- called from __tipc_nl_media_set() (MEDIA_SET)\n2. inline check in __tipc_nl_bearer_set() at bearer.c:1160 (BEARER_SET)\n\nFix both by rejecting MTU values above U16_MAX.",
"id": "GHSA-prmr-9j2x-c47h",
"modified": "2026-08-19T18:32:13Z",
"published": "2026-08-10T15:33:45Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-68297"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1b8fb5a20508bfb0db854e01214888c761b3a911"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8bfdfe0dbb36a650b7c4dec1aeae078319938a0b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c1cda72f6acec02ebd45d913bf8527ff77336ba6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dc4b577a083b361d25e118dc96d8281255ebe22c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dfdfd987f1917c84766e097a6120a1f3f1634940"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f02334a9e378f7e07232b26dc3d2ab353339f040"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f4013598b69457dbea350df52e52daea6faef8eb"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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