CyberSecBulletin
CVE-2026-68338NVD status: Received

Linux: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2026-68338 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions acb40ebfa5c4d62f84339fcbf713f2a9fd033a71, c820f4b7f2fa38f8769db0d0cefdd94e2721504d, 4628efbdc7affd094181f5263e65c1062e31f15f as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.14% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to acb40ebfa5c4d62f84339fcbf713f2a9fd033a71 or c820f4b7f2fa38f8769db0d0cefdd94e2721504d or 4628efbdc7affd094181f5263e65c1062e31f15f or 80ec024d53a05c60ad1d08968dcf745f10c1665c, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxdc99f600698dcac69b8f56dda9a8a00d645c5ffc up to, but not including, acb40ebfa5c4d62f84339fcbf713f2a9fd033a71; dc99f600698dcac69b8f56dda9a8a00d645c5ffc up to, but not including, c820f4b7f2fa38f8769db0d0cefdd94e2721504d; dc99f600698dcac69b8f56dda9a8a00d645c5ffc up to, but not including, 4628efbdc7affd094181f5263e65c1062e31f15f; dc99f600698dcac69b8f56dda9a8a00d645c5ffc up to, but not including, 80ec024d53a05c60ad1d08968dcf745f10c1665c; dc99f600698dcac69b8f56dda9a8a00d645c5ffc up to, but not including, 0a052e0808e015e68144a9877e6ef42b952c49fa; dc99f600698dcac69b8f56dda9a8a00d645c5ffc up to, but not including, 1bc55c29cd85818e9052f17deb287d5a11fb817f; dc99f600698dcac69b8f56dda9a8a00d645c5ffc up to, but not including, a885387dae7986a55bae5c77a15bdd447f64e9b9; dc99f600698dcac69b8f56dda9a8a00d645c5ffc up to, but not including, 50aff80475abd3533eef4320477037e6fcc6b56e; and 1 more rangesacb40ebfa5c4d62f84339fcbf713f2a9fd033a71, c820f4b7f2fa38f8769db0d0cefdd94e2721504d, 4628efbdc7affd094181f5263e65c1062e31f15f, 80ec024d53a05c60ad1d08968dcf745f10c1665c, 0a052e0808e015e68144a9877e6ef42b952c49fa, 1bc55c29cd85818e9052f17deb287d5a11fb817f

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

How developers prevent this class of flaw

  • In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
  • Use thread-safe capabilities such as the data access abstraction in Spring.
  • Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

More Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities (CWE-362)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities

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