CVE-2026-68297 (GCVE-0-2026-68297)
Vulnerability from cvelistv5
Published
2026-08-10 12:02
Modified
2026-08-19 16:32
Severity ?
VLAI Severity ?
EPSS score ?
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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 901271e0403af638c224987c2a4e55cebade7e91 Version: 901271e0403af638c224987c2a4e55cebade7e91 Version: 901271e0403af638c224987c2a4e55cebade7e91 Version: 901271e0403af638c224987c2a4e55cebade7e91 Version: 901271e0403af638c224987c2a4e55cebade7e91 Version: 901271e0403af638c224987c2a4e55cebade7e91 Version: 901271e0403af638c224987c2a4e55cebade7e91 Version: 901271e0403af638c224987c2a4e55cebade7e91 |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/tipc/netlink.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "8bfdfe0dbb36a650b7c4dec1aeae078319938a0b",
"status": "affected",
"version": "901271e0403af638c224987c2a4e55cebade7e91",
"versionType": "git"
},
{
"lessThan": "dc4b577a083b361d25e118dc96d8281255ebe22c",
"status": "affected",
"version": "901271e0403af638c224987c2a4e55cebade7e91",
"versionType": "git"
},
{
"lessThan": "dfdfd987f1917c84766e097a6120a1f3f1634940",
"status": "affected",
"version": "901271e0403af638c224987c2a4e55cebade7e91",
"versionType": "git"
},
{
"lessThan": "f02334a9e378f7e07232b26dc3d2ab353339f040",
"status": "affected",
"version": "901271e0403af638c224987c2a4e55cebade7e91",
"versionType": "git"
},
{
"lessThan": "f4013598b69457dbea350df52e52daea6faef8eb",
"status": "affected",
"version": "901271e0403af638c224987c2a4e55cebade7e91",
"versionType": "git"
},
{
"lessThan": "1b8fb5a20508bfb0db854e01214888c761b3a911",
"status": "affected",
"version": "901271e0403af638c224987c2a4e55cebade7e91",
"versionType": "git"
},
{
"lessThan": "c1cda72f6acec02ebd45d913bf8527ff77336ba6",
"status": "affected",
"version": "901271e0403af638c224987c2a4e55cebade7e91",
"versionType": "git"
},
{
"lessThan": "9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8",
"status": "affected",
"version": "901271e0403af638c224987c2a4e55cebade7e91",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/tipc/netlink.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "4.18"
},
{
"lessThan": "4.18",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.265",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.148",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.101",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.42",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.6",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.265",
"versionStartIncluding": "4.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.216",
"versionStartIncluding": "4.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.183",
"versionStartIncluding": "4.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.148",
"versionStartIncluding": "4.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.101",
"versionStartIncluding": "4.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.42",
"versionStartIncluding": "4.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.6",
"versionStartIncluding": "4.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.2",
"versionStartIncluding": "4.18",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 7.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:L - The attack begins with a local TIPC netlink command (TIPC_NL_BEARER_SET/TIPC_NL_MEDIA_SET) setting an out-of-range MTU, with the crash/corruption then triggered by locally generated discovery traffic and sendmsg() in the attacker\u0027s own network namespace.\nAC:L - The attacker fully controls both the bad MTU value and the discovery packet that creates the link, so the truncation and subsequent divide-by-zero or undersized-fragment path trigger deterministically on every attempt.\nPR:L - Both netlink ops are gated by GENL_UNS_ADMIN_PERM, i.e. CAP_NET_ADMIN in the owning user namespace, which any unprivileged user obtains via `unshare -Urn`; the commit message explicitly reports the crash reproduced as an unprivileged user through a user namespace.\nUI:N - The attacker performs every step (bearer setup, MTU configuration, packet injection, sendmsg) with no action from any other user or administrator.\nS:U - The truncated MTU corrupts only kernel state within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Truncated MTUs below the TIPC header size propagate into tipc_msg_build() as pktmax, driving negative fragment remainders and oversized copies into undersized skbs; the resulting heap corruption and adjacent-object exposure can be leveraged to read kernel memory.\nI:H - The undersized-fragment path writes INT_H_SIZE plus header bytes and then a negative-length (huge unsigned) user copy into a buffer allocated at the truncated MTU size, giving an attacker-controlled linear heap overflow suitable for control-flow hijacking.\nA:H - MTU values truncating to under 20 make tipc_link_set_queue_limits() divide by zero inside tipc_link_create(), which runs in softirq context from tipc_udp_recv()/tipc_disc_rcv(), producing a kernel oops that is typically fatal in interrupt context."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-19T16:32:46.091Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/8bfdfe0dbb36a650b7c4dec1aeae078319938a0b"
},
{
"url": "https://git.kernel.org/stable/c/dc4b577a083b361d25e118dc96d8281255ebe22c"
},
{
"url": "https://git.kernel.org/stable/c/dfdfd987f1917c84766e097a6120a1f3f1634940"
},
{
"url": "https://git.kernel.org/stable/c/f02334a9e378f7e07232b26dc3d2ab353339f040"
},
{
"url": "https://git.kernel.org/stable/c/f4013598b69457dbea350df52e52daea6faef8eb"
},
{
"url": "https://git.kernel.org/stable/c/1b8fb5a20508bfb0db854e01214888c761b3a911"
},
{
"url": "https://git.kernel.org/stable/c/c1cda72f6acec02ebd45d913bf8527ff77336ba6"
},
{
"url": "https://git.kernel.org/stable/c/9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8"
}
],
"title": "tipc: fix u16 MTU truncation in media and bearer MTU validation",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-68297",
"datePublished": "2026-08-10T12:02:30.721Z",
"dateReserved": "2026-07-30T09:28:09.380Z",
"dateUpdated": "2026-08-19T16:32:46.091Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
Loading…
Loading…
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
Loading…
Loading…