CVE-2026-31504 (GCVE-0-2026-31504)
Vulnerability from cvelistv5 – Published: 2026-04-22 13:54 – Updated: 2026-10-19 18:45
VLAI
EPSS
VEX
Title
net: fix fanout UAF in packet_release() via NETDEV_UP race
Summary
In the Linux kernel, the following vulnerability has been resolved:
net: fix fanout UAF in packet_release() via NETDEV_UP race
`packet_release()` has a race window where `NETDEV_UP` can re-register a
socket into a fanout group's `arr[]` array. The re-registration is not
cleaned up by `fanout_release()`, leaving a dangling pointer in the fanout
array.
`packet_release()` does NOT zero `po->num` in its `bind_lock` section.
After releasing `bind_lock`, `po->num` is still non-zero and `po->ifindex`
still matches the bound device. A concurrent `packet_notifier(NETDEV_UP)`
that already found the socket in `sklist` can re-register the hook.
For fanout sockets, this re-registration calls `__fanout_link(sk, po)`
which adds the socket back into `f->arr[]` and increments `f->num_members`,
but does NOT increment `f->sk_ref`.
The fix sets `po->num` to zero in `packet_release` while `bind_lock` is
held to prevent NETDEV_UP from linking, preventing the race window.
This bug was found following an additional audit with Claude Code based
on CVE-2025-38617.
Severity
7.8 (High)
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 15:10 UTC
CWE
- CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Assigner
References
11 references
Impacted products
11 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < ee642b1962caa9aa231c01abbd58bc453ae6b66e
(git)
Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < 42cfd7898eeed290c9fb73f732af1f7d6b0a703e (git) Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < 1b4c03f8892d955385c202009af7485364731bb9 (git) Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < 654386baef228c2992dbf604c819e4c7c35fc71b (git) Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < 75fe6db23705a1d55160081f7b37db9665b1880b (git) Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6 (git) Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < ceccbfc6de720ad633519a226715989cfb065af1 (git) Affected: ce06b03e60fc19c680d1bf873e779bf11c2fc518 , < 42156f93d123436f2a27c468f18c966b7e5db796 (git) |
guessed | |
| Linux | Linux |
Affected:
3.1
Unaffected: 0 , < 3.1 (semver) Unaffected: 5.10.253 , ≤ 5.10.* (semver) Unaffected: 5.15.203 , ≤ 5.15.* (semver) Unaffected: 6.1.168 , ≤ 6.1.* (semver) Unaffected: 6.6.131 , ≤ 6.6.* (semver) Unaffected: 6.12.80 , ≤ 6.12.* (semver) Unaffected: 6.18.21 , ≤ 6.18.* (semver) Unaffected: 6.19.11 , ≤ 6.19.* (semver) Unaffected: 7.0 , ≤ * (original_commit_for_fix) |
guessed | |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.6 , < *
(custom)
|
guessed | |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.5 , < *
(custom)
|
guessed | |
| Siemens | SIMATIC S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.7 , < *
(custom)
|
guessed | |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP |
Affected:
V3.1.6 , < *
(custom)
|
guessed | |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP |
Affected:
V3.1.5 , < *
(custom)
|
guessed | |
| Siemens | SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP |
Affected:
V3.1.7 , < *
(custom)
|
guessed | |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.6 , < *
(custom)
|
guessed | |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.5 , < *
(custom)
|
guessed | |
| Siemens | SIPLUS S7-1500 CPU 1518-4 PN/DP MFP |
Affected:
V3.1.7 , < *
(custom)
|
guessed |
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{
"Automatable": "no"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-16T15:10:18.282904Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-362",
"description": "CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization (\u0027Race Condition\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-16T15:10:18.855Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/packet/af_packet.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "ee642b1962caa9aa231c01abbd58bc453ae6b66e",
"status": "affected",
"version": "ce06b03e60fc19c680d1bf873e779bf11c2fc518",
"versionType": "git"
},
{
"lessThan": "42cfd7898eeed290c9fb73f732af1f7d6b0a703e",
"status": "affected",
"version": "ce06b03e60fc19c680d1bf873e779bf11c2fc518",
"versionType": "git"
},
{
"lessThan": "1b4c03f8892d955385c202009af7485364731bb9",
"status": "affected",
"version": "ce06b03e60fc19c680d1bf873e779bf11c2fc518",
"versionType": "git"
},
{
"lessThan": "654386baef228c2992dbf604c819e4c7c35fc71b",
"status": "affected",
"version": "ce06b03e60fc19c680d1bf873e779bf11c2fc518",
"versionType": "git"
},
{
"lessThan": "75fe6db23705a1d55160081f7b37db9665b1880b",
"status": "affected",
"version": "ce06b03e60fc19c680d1bf873e779bf11c2fc518",
"versionType": "git"
},
{
"lessThan": "d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6",
"status": "affected",
"version": "ce06b03e60fc19c680d1bf873e779bf11c2fc518",
"versionType": "git"
},
{
"lessThan": "ceccbfc6de720ad633519a226715989cfb065af1",
"status": "affected",
"version": "ce06b03e60fc19c680d1bf873e779bf11c2fc518",
"versionType": "git"
},
{
"lessThan": "42156f93d123436f2a27c468f18c966b7e5db796",
"status": "affected",
"version": "ce06b03e60fc19c680d1bf873e779bf11c2fc518",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/packet/af_packet.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "3.1"
},
{
"lessThan": "3.1",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.253",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.203",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.168",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.131",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.80",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.21",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.19.*",
"status": "unaffected",
"version": "6.19.11",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.0",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.253",
"versionStartIncluding": "3.1",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.15.203",
"versionStartIncluding": "3.1",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.1.168",
"versionStartIncluding": "3.1",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.131",
"versionStartIncluding": "3.1",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.80",
"versionStartIncluding": "3.1",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.21",
"versionStartIncluding": "3.1",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.19.11",
"versionStartIncluding": "3.1",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.0",
"versionStartIncluding": "3.1",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: fix fanout UAF in packet_release() via NETDEV_UP race\n\n`packet_release()` has a race window where `NETDEV_UP` can re-register a\nsocket into a fanout group\u0027s `arr[]` array. The re-registration is not\ncleaned up by `fanout_release()`, leaving a dangling pointer in the fanout\narray.\n`packet_release()` does NOT zero `po-\u003enum` in its `bind_lock` section.\nAfter releasing `bind_lock`, `po-\u003enum` is still non-zero and `po-\u003eifindex`\nstill matches the bound device. A concurrent `packet_notifier(NETDEV_UP)`\nthat already found the socket in `sklist` can re-register the hook.\nFor fanout sockets, this re-registration calls `__fanout_link(sk, po)`\nwhich adds the socket back into `f-\u003earr[]` and increments `f-\u003enum_members`,\nbut does NOT increment `f-\u003esk_ref`.\n\nThe fix sets `po-\u003enum` to zero in `packet_release` while `bind_lock` is\nheld to prevent NETDEV_UP from linking, preventing the race window.\n\nThis bug was found following an additional audit with Claude Code based\non CVE-2025-38617."
}
],
"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 vulnerable path is reached through local AF_PACKET socket setup, setsockopt(PACKET_FANOUT), close(), and local NETDEV_UP triggering, not by unauthenticated remote packets alone.\nAC:L - The attacker controls both sides of the race by closing/releasing AF_PACKET fanout sockets while concurrently toggling a controlled netdevice up, and can repeat the race with chosen fanout modes.\nPR:L - AF_PACKET creation requires CAP_NET_RAW and NETDEV_UP requires CAP_NET_ADMIN in the target network namespace; both are obtainable by an unprivileged user in a user/network namespace on affected systems.\nUI:N - No victim action is required once the local attacker can run code and issue the relevant syscalls.\nS:U - The bug corrupts kernel networking state and enables kernel compromise within the same kernel security authority; it is not a VM or hardware boundary escape.\nC:H - This is a kernel heap use-after-free involving stale packet fanout/socket pointers reachable from packet receive dispatch, and such UAFs can be shaped into kernel memory disclosure primitives.\nI:H - The dangling fanout entry can drive execution through freed or reclaimed packet socket state, making kernel memory corruption and control-flow or privilege-escalation primitives defensible.\nA:H - Even without full exploitation, the stale fanout/socket pointer can be dereferenced on packet delivery and cause a kernel oops, panic, or persistent crash."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-05T12:23:07.003Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/ee642b1962caa9aa231c01abbd58bc453ae6b66e"
},
{
"url": "https://git.kernel.org/stable/c/42cfd7898eeed290c9fb73f732af1f7d6b0a703e"
},
{
"url": "https://git.kernel.org/stable/c/1b4c03f8892d955385c202009af7485364731bb9"
},
{
"url": "https://git.kernel.org/stable/c/654386baef228c2992dbf604c819e4c7c35fc71b"
},
{
"url": "https://git.kernel.org/stable/c/75fe6db23705a1d55160081f7b37db9665b1880b"
},
{
"url": "https://git.kernel.org/stable/c/d0c7cdc15fdf8c4f91aca1928e52295d175b6ec6"
},
{
"url": "https://git.kernel.org/stable/c/ceccbfc6de720ad633519a226715989cfb065af1"
},
{
"url": "https://git.kernel.org/stable/c/42156f93d123436f2a27c468f18c966b7e5db796"
}
],
"title": "net: fix fanout UAF in packet_release() via NETDEV_UP race",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-31504",
"datePublished": "2026-04-22T13:54:23.862Z",
"dateReserved": "2026-03-09T15:48:24.105Z",
"dateUpdated": "2026-10-19T18:45:53.946Z",
"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
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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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.