CyberSecBulletin
CVE-2026-68329NVD status: Received

Linux: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2026-68329 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 8.8 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 82c9a749d44efaaa1a1c781f8a6cf1747718f228, ab7faf5a172ebfdc423ebb3eea4d472740de82f9, 93494bd446396c257fb589f59894577e96e406e2 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 0.13% 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 82c9a749d44efaaa1a1c781f8a6cf1747718f228 or ab7faf5a172ebfdc423ebb3eea4d472740de82f9 or 93494bd446396c257fb589f59894577e96e406e2 or d053eb7e09e10cbdca3fca8b35c1017d438091b2, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux815b33fdc279d34ab40a8bfe1866623a4cc5669b up to, but not including, 82c9a749d44efaaa1a1c781f8a6cf1747718f228; 815b33fdc279d34ab40a8bfe1866623a4cc5669b up to, but not including, ab7faf5a172ebfdc423ebb3eea4d472740de82f9; 815b33fdc279d34ab40a8bfe1866623a4cc5669b up to, but not including, 93494bd446396c257fb589f59894577e96e406e2; 815b33fdc279d34ab40a8bfe1866623a4cc5669b up to, but not including, d053eb7e09e10cbdca3fca8b35c1017d438091b2; 815b33fdc279d34ab40a8bfe1866623a4cc5669b up to, but not including, 02f8cefa2ad95ea3754f0cfd6fbae7f866202ccb; 815b33fdc279d34ab40a8bfe1866623a4cc5669b up to, but not including, 1e75a8255f11c81fb07e81e5029cfd75804350a0; 3.082c9a749d44efaaa1a1c781f8a6cf1747718f228, ab7faf5a172ebfdc423ebb3eea4d472740de82f9, 93494bd446396c257fb589f59894577e96e406e2, d053eb7e09e10cbdca3fca8b35c1017d438091b2, 02f8cefa2ad95ea3754f0cfd6fbae7f866202ccb, 1e75a8255f11c81fb07e81e5029cfd75804350a0

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
ChangedThe attack can reach beyond the vulnerable component into other systems.
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:C/C:H/I:H/A:H. Scored by CNA.

Official description

In the Linux kernel, the following vulnerability has been resolved: iommu/amd: Wait for completion instead of returning early in iommu_completion_wait() need_sync is a per-IOMMU flag shared by all domains and devices behind that IOMMU. It is set whenever a command is queued with sync == true and cleared when a completion-wait (CWAIT) command is queued. However, a cleared need_sync only means that a covering CWAIT has been queued, not that all previously queued commands have actually completed in hardware. iommu_completion_wait() read need_sync locklessly and returned early when it was false. This breaks the "block until all previously queued commands have completed" contract in a multi-CPU scenario: CPU2: queue inv-B => need_sync = true CPU1: queue CWAIT(N); need_sync = false; then wait_on_sem(N) CPU2: read need_sync == false => return 0 (no wait!) CPU2 returns without waiting for any sequence number even though its inv-B may not have completed yet (CWAIT(N), queued after inv-B, has not been signaled). CPU2 then proceeds to, for example, free page-table pages while the IOMMU can still walk stale translations, opening a use-after-free window. This is a logical race in the meaning of the flag, not a memory-visibility issue, so barriers alone do not help. Fix it without losing the optimization of avoiding redundant CWAIT commands: take iommu->lock before testing need_sync, and when it is false do not return early but wait for the last allocated sequence number (cmd_sem_val). Since need_sync == false implies no sync command was queued after the last CWAIT, that CWAIT is FIFO-ordered after every not-yet-completed command, so waiting for its sequence number guarantees all prior commands (possibly queued by another CPU) have completed. The common path with pending work is unchanged and no extra hardware command is issued.

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

Spotted an error? Tell us.