CVE-2026-74496 (GCVE-0-2026-74496)
Vulnerability from cvelistv5 – Published: 2026-08-15 12:27 – Updated: 2026-10-16 19:05
VLAI
EPSS
VEX
Title
fou: Fix use-after-free in fou_create()
Summary
In the Linux kernel, the following vulnerability has been resolved:
fou: Fix use-after-free in fou_create()
fou_create() publishes struct fou through sk_user_data before adding the
new FOU port to the per-netns list. If fou_add_to_port_list() fails,
the error path frees fou while it is still reachable through
sk_user_data. A concurrent receive can then dereference the freed
object in fou_from_sock().
This ordering issue was previously noted in the linked discussion.
The failure is reachable when local port 0 is requested. Each socket
binds to a different ephemeral port, but fou_cfg_cmp() compares the
requested port 0 and reports -EALREADY once an entry already exists.
Release the tunnel socket before freeing fou so sk_user_data is cleared
first, and defer reclamation with kfree_rcu() to protect concurrent RCU
readers. This matches the lifetime handling in fou_release().
Severity
7.8 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 18:58 UTC
Assigner
References
8 references
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
23461551c00628c3f3fe9cf837bf53cf8f212b63 , < 0ee628a58d83e571f36ec9f07624d6845e420c50
(git)
Affected: 23461551c00628c3f3fe9cf837bf53cf8f212b63 , < a6fca682cfa2041e31aa72cc397c4a1406eb7468 (git) Affected: 23461551c00628c3f3fe9cf837bf53cf8f212b63 , < b3f9c3e60aa25453774f899d25b5e61dd0bec1d5 (git) Affected: 23461551c00628c3f3fe9cf837bf53cf8f212b63 , < 99f4d3120b244f92e5df787152041296a2860cb5 (git) Affected: 23461551c00628c3f3fe9cf837bf53cf8f212b63 , < 58835985c035a8333742f829ad7e0889a082f9d3 (git) Affected: 23461551c00628c3f3fe9cf837bf53cf8f212b63 , < 9042867d4701728f0c6527215b11471759904d8f (git) Affected: 23461551c00628c3f3fe9cf837bf53cf8f212b63 , < a28d8903bfe76089ea4bbdbff9976965f9ef8107 (git) Affected: 23461551c00628c3f3fe9cf837bf53cf8f212b63 , < b14361aca6350ff7907b0e9903c7b94dc7d5d4a0 (git) |
guessed | |
| Linux | Linux |
Affected:
3.18
Unaffected: 0 , < 3.18 (semver) Unaffected: 5.10.271 , ≤ 5.10.* (semver) Unaffected: 5.15.222 , ≤ 5.15.* (semver) Unaffected: 6.1.189 , ≤ 6.1.* (semver) Unaffected: 6.6.158 , ≤ 6.6.* (semver) Unaffected: 6.12.111 , ≤ 6.12.* (semver) Unaffected: 6.18.53 , ≤ 6.18.* (semver) Unaffected: 7.1.8 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix) |
guessed |
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"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-08-21T07:57:43+00:00",
"cve": "CVE-2026-74496",
"id": "CVE-2026-74496",
"initial_release_date": "2026-08-15T00:00:00+00:00",
"product_status:known_affected": "184",
"product_status:known_not_affected": "90",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: fou: Fix use-after-free in fou_create()",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74496.json",
"version": "3"
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-74496",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-16T18:58:18.343359Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-10-16T18:58:18.987Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/ipv4/fou_core.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "0ee628a58d83e571f36ec9f07624d6845e420c50",
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"versionType": "git"
},
{
"lessThan": "a6fca682cfa2041e31aa72cc397c4a1406eb7468",
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"versionType": "git"
},
{
"lessThan": "b3f9c3e60aa25453774f899d25b5e61dd0bec1d5",
"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"versionType": "git"
},
{
"lessThan": "99f4d3120b244f92e5df787152041296a2860cb5",
"status": "affected",
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"versionType": "git"
},
{
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"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"versionType": "git"
},
{
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"status": "affected",
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},
{
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"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"versionType": "git"
},
{
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"status": "affected",
"version": "23461551c00628c3f3fe9cf837bf53cf8f212b63",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/ipv4/fou_core.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "3.18"
},
{
"lessThan": "3.18",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.271",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.222",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.189",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.158",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.111",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.53",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.8",
"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": "5.10.271",
"versionStartIncluding": "3.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.222",
"versionStartIncluding": "3.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.189",
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.158",
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.53",
"versionStartIncluding": "3.18",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1.8",
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"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "3.18",
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}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfou: Fix use-after-free in fou_create()\n\nfou_create() publishes struct fou through sk_user_data before adding the\nnew FOU port to the per-netns list. If fou_add_to_port_list() fails,\nthe error path frees fou while it is still reachable through\nsk_user_data. A concurrent receive can then dereference the freed\nobject in fou_from_sock().\n\nThis ordering issue was previously noted in the linked discussion.\n\nThe failure is reachable when local port 0 is requested. Each socket\nbinds to a different ephemeral port, but fou_cfg_cmp() compares the\nrequested port 0 and reports -EALREADY once an entry already exists.\n\nRelease the tunnel socket before freeing fou so sk_user_data is cleared\nfirst, and defer reclamation with kfree_rcu() to protect concurrent RCU\nreaders. This matches the lifetime handling in fou_release()."
}
],
"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 UAF is opened only via local FOU_CMD_ADD genetlink into fou_create(); remote UDP can race the dangling sk_user_data read in fou_udp_recv/gue_udp_recv but cannot alone reach the erroneous teardown path.\nAC:L - An attacker with CAP_NET_ADMIN controls both sides: issue a second FOU_CMD_ADD with port 0 to force -EALREADY on fou_add_to_port_list while concurrently sending UDP/GRO traffic to the just-bound ephemeral socket during the kfree window.\nPR:L - FOU_CMD_ADD is gated by GENL_ADMIN_PERM (CAP_NET_ADMIN); the fou genl family is netnsok, so a user with CAP_NET_ADMIN inside unshare -Urn can configure FOU and trigger the failing add path without init-namespace root.\nUI:N - Exploitation is fully programmatic via concurrent netlink FOU_CMD_ADD requests and attacker-controlled UDP packets; no victim mount, file open, or other interactive action is required.\nS:U - Impact is kernel heap corruption and privilege escalation within the same security authority; this is not a VM escape, IOMMU bypass, or other cross-boundary scope change.\nC:H - Concurrent readers call fou_from_sock() and dereference freed struct fou fields (family, protocol, flags); reclaimed slab contents give attacker-controlled reads and kernel pointer disclosure primitives typical of UAF.\nI:H - Freed struct fou is attacker-reclaimable kmalloc memory; fou_gro_receive indexes inet_offloads[fou-\u003eprotocol] from the dangling pointer, enabling heap grooming for arbitrary writes and control-flow hijack.\nA:H - Use-after-free in UDP receive/GRO softirq reliably causes KASAN violations and, on production kernels, invalid pointer dereferences or panics when accessing the freed fou object during packet processing."
}
]
}
],
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"dateUpdated": "2026-10-03T10:56:03.355Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"references": [
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"url": "https://git.kernel.org/stable/c/0ee628a58d83e571f36ec9f07624d6845e420c50"
},
{
"url": "https://git.kernel.org/stable/c/a6fca682cfa2041e31aa72cc397c4a1406eb7468"
},
{
"url": "https://git.kernel.org/stable/c/b3f9c3e60aa25453774f899d25b5e61dd0bec1d5"
},
{
"url": "https://git.kernel.org/stable/c/99f4d3120b244f92e5df787152041296a2860cb5"
},
{
"url": "https://git.kernel.org/stable/c/58835985c035a8333742f829ad7e0889a082f9d3"
},
{
"url": "https://git.kernel.org/stable/c/9042867d4701728f0c6527215b11471759904d8f"
},
{
"url": "https://git.kernel.org/stable/c/a28d8903bfe76089ea4bbdbff9976965f9ef8107"
},
{
"url": "https://git.kernel.org/stable/c/b14361aca6350ff7907b0e9903c7b94dc7d5d4a0"
}
],
"title": "fou: Fix use-after-free in fou_create()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-74496",
"datePublished": "2026-08-15T12:27:23.854Z",
"dateReserved": "2026-08-15T05:44:03.906Z",
"dateUpdated": "2026-10-16T19:05:50.395Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.