CVE-2026-98955
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: flow_dissector: avoid u16 truncation of skb->len when computing thoff __skb_flow_dissect() computes key_control->thoff using: key_control->thoff = min_t(u16, nhoff, skb ? skb->len : hlen); min_t(u16, ...) casts both arguments to u16 before comparing them. Whenever skb->len (or hlen) modulo 65536 is smaller than nhoff, the truncated length wins and thoff is set to a bogus small value, even when the dissection succeeded. For example, an IPv4/TCP frame with skb->len == 65540 and nhoff == 34 gets thoff == 4, so callers such as skb_probe_transport_header() point the transport header inside the Ethernet header. Such skbs are not exotic: - At the time of commit d0c081b49137 ("flow_dissector: properly cap thoff field"), AF_PACKET with PACKET_VNET_HDR could already build GSO skbs larger than 64KB (MTU checks are skipped for GSO, and alloc_skb_with_frags() accepted up to MAX_SKB_FRAGS (17) order-0 pages on top of the linear part). - BIG TCP now makes skbs larger than 64KB common. - The following patch makes tun_get_user() dissect IFF_TAP frames before eth_type_trans() pulls the Ethernet header, so a GSO frame carrying a 65522..65535 byte L3 packet will be dissected with skb->len in [65536, 65549]. Compare as u32 instead. If the resulting offset cannot be represented in the u16 key_control->thoff, cap it to U16_MAX and report the dissection as failed rather than silently returning a wrong transport offset. thoff is still set on failure, as some callers (such as eth_get_headlen()) use it regardless of the return value.
View original CVE JSON
{
"id": "CVE-2026-98955",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-10-23T13:17:16.740",
"lastModified": "2026-10-30T13:21:32.687",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nflow_dissector: avoid u16 truncation of skb->len when computing thoff\n\n__skb_flow_dissect() computes key_control->thoff using:\n\n key_control->thoff = min_t(u16, nhoff, skb ? skb->len : hlen);\n\nmin_t(u16, ...) casts both arguments to u16 before comparing them.\nWhenever skb->len (or hlen) modulo 65536 is smaller than nhoff, the\ntruncated length wins and thoff is set to a bogus small value, even\nwhen the dissection succeeded. For example, an IPv4/TCP frame with\nskb->len == 65540 and nhoff == 34 gets thoff == 4, so callers such as\nskb_probe_transport_header() point the transport header inside the\nEthernet header.\n\nSuch skbs are not exotic:\n- At the time of commit d0c081b49137 (\"flow_dissector: properly cap\n thoff field\"), AF_PACKET with PACKET_VNET_HDR could already build GSO\n skbs larger than 64KB (MTU checks are skipped for GSO, and\n alloc_skb_with_frags() accepted up to MAX_SKB_FRAGS (17) order-0\n pages on top of the linear part).\n- BIG TCP now makes skbs larger than 64KB common.\n- The following patch makes tun_get_user() dissect IFF_TAP frames\n before eth_type_trans() pulls the Ethernet header, so a GSO frame\n carrying a 65522..65535 byte L3 packet will be dissected with\n skb->len in [65536, 65549].\n\nCompare as u32 instead. If the resulting offset cannot be represented\nin the u16 key_control->thoff, cap it to U16_MAX and report the\ndissection as failed rather than silently returning a wrong transport\noffset. thoff is still set on failure, as some callers (such as\neth_get_headlen()) use it regardless of the return value."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"net/core/flow_dissector.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "d0c081b49137cd3200f2023c0875723be66e7ce5",
"lessThan": "3f6000fdf8a57b9786669869af8a3e050b541bf3",
"versionType": "git",
"status": "affected"
},
{
"version": "d0c081b49137cd3200f2023c0875723be66e7ce5",
"lessThan": "2c2f82b696c5e877f60ea77b7784e906a5e63014",
"versionType": "git",
"status": "affected"
},
{
"version": "d0c081b49137cd3200f2023c0875723be66e7ce5",
"lessThan": "d44e66f5dd99319a32e378b610af7fcf78da985a",
"versionType": "git",
"status": "affected"
},
{
"version": "d0c081b49137cd3200f2023c0875723be66e7ce5",
"lessThan": "d9e08836d06c84abb18470c94b12b131eaccdc7d",
"versionType": "git",
"status": "affected"
},
{
"version": "d0c081b49137cd3200f2023c0875723be66e7ce5",
"lessThan": "50d0cd575cab763f833d6ac6eb6550b23a0b3dae",
"versionType": "git",
"status": "affected"
},
{
"version": "d0c081b49137cd3200f2023c0875723be66e7ce5",
"lessThan": "9993e6a0ac1b5b3101ffba702cacb9f42b9909d8",
"versionType": "git",
"status": "affected"
},
{
"version": "d0c081b49137cd3200f2023c0875723be66e7ce5",
"lessThan": "52efce4755a4b8b82039caa773645ffc80b25362",
"versionType": "git",
"status": "affected"
},
{
"version": "d0c081b49137cd3200f2023c0875723be66e7ce5",
"lessThan": "99bda1ecbd56905f8bd934b9cdccd3bd251192b1",
"versionType": "git",
"status": "affected"
},
{
"version": "d35cd5e279881ec36ff8cd82a2d9caebc0cce3fc",
"versionType": "git",
"status": "affected"
},
{
"version": "eecfa2eeefe3caef4c8d6b2284f6066c76ab26a1",
"versionType": "git",
"status": "affected"
},
{
"version": "80f327285cab6ab8e10c3ea03278add5dd99fb02",
"versionType": "git",
"status": "affected"
},
{
"version": "4.4.114",
"lessThan": "4.5",
"versionType": "semver",
"status": "affected"
},
{
"version": "4.9.79",
"lessThan": "4.10",
"versionType": "semver",
"status": "affected"
},
{
"version": "4.14.16",
"lessThan": "4.15",
"versionType": "semver",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"net/core/flow_dissector.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "4.15",
"status": "affected"
},
{
"version": "0",
"lessThan": "4.15",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.10.273",
"lessThanOrEqual": "5.10.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.15.224",
"lessThanOrEqual": "5.15.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.1.191",
"lessThanOrEqual": "6.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.6.160",
"lessThanOrEqual": "6.6.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.113",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.57",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2.11",
"lessThanOrEqual": "7.2.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.3",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {},
"references": [
{
"url": "https://git.kernel.org/stable/c/2c2f82b696c5e877f60ea77b7784e906a5e63014",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/3f6000fdf8a57b9786669869af8a3e050b541bf3",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/50d0cd575cab763f833d6ac6eb6550b23a0b3dae",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/52efce4755a4b8b82039caa773645ffc80b25362",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/9993e6a0ac1b5b3101ffba702cacb9f42b9909d8",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/99bda1ecbd56905f8bd934b9cdccd3bd251192b1",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/d44e66f5dd99319a32e378b610af7fcf78da985a",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/d9e08836d06c84abb18470c94b12b131eaccdc7d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
]
}