flow_dissector: avoid u16 truncation of skb->len when computing thoff
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 stil
CVE-2026-98955
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-98955
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"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"
}
],
"programFiles": [
"net/core/flow_dissector.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.15"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.15",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.113",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.57",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.11",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/core/flow_dissector.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-98955
Source reference:
/cveMetadata/cveId
Publisher severity
No explicit severity was provided.
- Event
- #52810 · Revision 1
- Added to Heist Feed
- Publisher date