Description
In the Linux kernel, the following vulnerability has been resolved:

net/packet: avoid fanout hook re-registration after unregister

packet_set_ring() temporarily detaches a socket from packet delivery while
reconfiguring its ring. It records the previous running state, clears
po->num, unregisters the protocol hook when needed, drops po->bind_lock,
and later restores po->num and re-registers the hook from the saved
was_running value.

That unlocked window can race with NETDEV_UNREGISTER. The notifier can
observe the socket as not running, skip __unregister_prot_hook(), and
invalidate the per-socket binding by setting po->ifindex to -1 and clearing
po->prot_hook.dev. A one-member fanout group can still retain its shared
fanout hook device pointer. When packet_set_ring() resumes, re-registering
solely from the stale was_running state can re-add the fanout hook after
the device has been unregistered.

Treat po->ifindex == -1 as an invalidated binding after reacquiring
po->bind_lock. This is distinct from ifindex 0, the normal
unbound/wildcard state: ifindex -1 marks an existing device binding that
was invalidated when the device was unregistered. Restore po->num as
before, but do not re-register the hook if device unregister already
detached the socket.
Published: 2026-08-10
Score: 7.8 High
EPSS: < 1% Very Low
KEV: No
Impact: Denial of Service via packet_set_ring race leading to re‑registration of a fanout hook after device unregistration
Action: Patch
AI Analysis

Impact

A race condition occurs in the Linux kernel net/packet subsystem when the packet_set_ring function reallocates a socket’s ring. While the socket’s hook is temporarily detached, a NETDEV_UNREGISTER notifier can change the socket state and invalidate the device binding. When packet_set_ring later resumes, it may re‑register the hook using stale state, allowing the socket to bind to a device that has already been unregistered. This logic flaw can lead to loss of packet routing, effectively providing a denial‑of‑service to network services that rely on that socket.

Affected Systems

The vulnerability affects all Linux kernel builds that include the unpatched packet_set_ring implementation referenced in the commit series. No specific kernel major/minor versions are listed in the data; the fix is aggregated across the Linux kernel code base.

Risk and Exploitability

Based on the description, it is inferred that the race condition could be triggered by a local actor with sufficient privileges to create sockets and initiate NETDEV_UNREGISTER. The CVSS score is 7.8 and the EPSS score is < 1%, and the vulnerability is not listed in the CISA KEV catalog. Because the description does not specify a remote exploitation path, remote attackers are unlikely to gain direct access; the attack thus requires local privileged exploitation. If successfully triggered, the kernel may re‑register a fanout hook after the device has been unregistered, potentially leading to loss of packet routing and a denial‑of‑service or kernel instability. The absence of public exploit references suggests a moderate exploitation probability, but the impact on stability means the risk remains significant for systems that see untrusted network traffic.

Generated by OpenCVE AI on October 20, 2026 at 10:42 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Update the Linux kernel to a version that includes the packet_set_ring fix, ensuring the commit that guards against re‑registration after device unregistration is present.
  • Verify that any custom network drivers or modules are also updated to match the patched kernel version, thereby preventing residual race conditions.
  • If immediate kernel upgrade is not feasible, enforce stricter permission controls on network device unregistration and monitor kernel logs for failures indicative of this race condition.

Generated by OpenCVE AI on October 20, 2026 at 10:42 UTC.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-4745-1 linux-6.12 security update
Debian DLA Debian DLA DLA-4777-1 linux security update
Ubuntu USN Ubuntu USN USN-8876-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8875-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8877-1 Linux kernel (GCP) vulnerabilities
Ubuntu USN Ubuntu USN USN-8878-1 Linux kernel (GCP) vulnerabilities
Ubuntu USN Ubuntu USN USN-8879-1 Linux kernel (Oracle) vulnerabilities
Ubuntu USN Ubuntu USN USN-8887-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8888-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8889-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8887-2 Linux kernel (AWS) vulnerabilities
Ubuntu USN Ubuntu USN USN-8888-2 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-8875-2 Linux kernel (NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-8887-3 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8917-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8918-1 Linux kernel (Azure) vulnerabilities
History

Mon, 19 Oct 2026 22:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-362
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Wed, 19 Aug 2026 16:45:00 +0000


Thu, 13 Aug 2026 23:15:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 4.7, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}


Thu, 13 Aug 2026 05:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-362

Wed, 12 Aug 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-367
References
Metrics threat_severity

None

cvssV3_1

{'score': 4.7, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Moderate


Mon, 10 Aug 2026 16:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-362

Mon, 10 Aug 2026 12:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: net/packet: avoid fanout hook re-registration after unregister packet_set_ring() temporarily detaches a socket from packet delivery while reconfiguring its ring. It records the previous running state, clears po->num, unregisters the protocol hook when needed, drops po->bind_lock, and later restores po->num and re-registers the hook from the saved was_running value. That unlocked window can race with NETDEV_UNREGISTER. The notifier can observe the socket as not running, skip __unregister_prot_hook(), and invalidate the per-socket binding by setting po->ifindex to -1 and clearing po->prot_hook.dev. A one-member fanout group can still retain its shared fanout hook device pointer. When packet_set_ring() resumes, re-registering solely from the stale was_running state can re-add the fanout hook after the device has been unregistered. Treat po->ifindex == -1 as an invalidated binding after reacquiring po->bind_lock. This is distinct from ifindex 0, the normal unbound/wildcard state: ifindex -1 marks an existing device binding that was invalidated when the device was unregistered. Restore po->num as before, but do not re-register the hook if device unregister already detached the socket.
Title net/packet: avoid fanout hook re-registration after unregister
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-10-19T21:09:05.428Z

Reserved: 2026-07-30T09:28:09.384Z

Link: CVE-2026-68338

cve-icon Vulnrichment

Updated: 2026-10-16T15:47:17.184Z

cve-icon NVD

Status : Received

Published: 2026-08-10T13:20:24.230

Modified: 2026-10-19T22:17:13.900

Link: CVE-2026-68338

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-08-10T12:03:14Z

Links: CVE-2026-68338 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-20T10:45:13Z

Weaknesses
  • CWE-362

    Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

  • CWE-367

    Time-of-check Time-of-use (TOCTOU) Race Condition