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fou: Fix use-after-free in fou_create()

Type: advisorySources: OSV

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().

Products
Kernel
Affected versions
Not specified
Fixed versions
5.10.271, 5.15.222, 6.1.189, 6.12.111, 6.18.53, 6.6.158, 7.1.8
CVEs
CVE-2026-74496
Confirmed fixed CVEs
Not specified
Updated in this feed
5 Nov 2026, 16:49 UTC · Revision 1

Source evidence

fou: Fix use-after-free in fou_create()

core-osv · Original source

Published 15 Aug 2026, 12:27 UTC

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().

osv:CVE-2026-74496

Kernel

Fixed versions: 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.111, 6.18.53, 7.1.8

Complete source record
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  "url": "https://osv.dev/vulnerability/CVE-2026-74496",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "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().",
    "evidence": "osv:CVE-2026-74496",
    "products": [
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      "modified": "2026-10-28T02:30:44.416010641Z",
      "provider": "osv",
      "references": [
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        "https://git.kernel.org/stable/c/58835985c035a8333742f829ad7e0889a082f9d3",
        "https://git.kernel.org/stable/c/9042867d4701728f0c6527215b11471759904d8f",
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        "https://git.kernel.org/stable/c/b3f9c3e60aa25453774f899d25b5e61dd0bec1d5",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74496.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-74496",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
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      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74496.json"
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    },
    "related_cves": [
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 512457,
  "published_at": "2026-08-15T12:27:23.854+00:00"
}