CyberSecBulletin
CVE-2026-64600NVD status: Modified

Linux: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2026-64600 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 dc11be133efca5fe3a2fb02b016dee825cc12f18, b8c9aa832b52680ee40d6cab0efb081f9a69df05, 50f0012da1040f69a4e788cd9aed587c9a04983f 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 0.47% 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 dc11be133efca5fe3a2fb02b016dee825cc12f18 or b8c9aa832b52680ee40d6cab0efb081f9a69df05 or 50f0012da1040f69a4e788cd9aed587c9a04983f or e705d81a7193dd19e69b8e2bad4696d78a4ea075, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.15.212 or 6.1.178 or 6.6.145 or 6.12.96, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 up to, but not including, dc11be133efca5fe3a2fb02b016dee825cc12f18; 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 up to, but not including, b8c9aa832b52680ee40d6cab0efb081f9a69df05; 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 up to, but not including, 50f0012da1040f69a4e788cd9aed587c9a04983f; 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 up to, but not including, e705d81a7193dd19e69b8e2bad4696d78a4ea075; 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 up to, but not including, 206c09b04dc5469c7ff14d8aceff2d47c88078d9; 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 up to, but not including, 44f891bc088958399eec27f7604928694aa35581; 3c68d44a2b49a0ac9165faa9c191e1e618c8a8d5 up to, but not including, 2f4acd0fcd862e22eab45690ec2c08c80b6ef2e7; 4.11dc11be133efca5fe3a2fb02b016dee825cc12f18, b8c9aa832b52680ee40d6cab0efb081f9a69df05, 50f0012da1040f69a4e788cd9aed587c9a04983f, e705d81a7193dd19e69b8e2bad4696d78a4ea075, 206c09b04dc5469c7ff14d8aceff2d47c88078d9, 44f891bc088958399eec27f7604928694aa35581
LinuxLinux Kernel4.11 up to, but not including, 5.15.212; 5.16 up to, but not including, 6.1.178; 6.2 up to, but not including, 6.6.145; 6.7 up to, but not including, 6.12.96; 6.13 up to, but not including, 6.18.39; 6.19 up to, but not including, 7.1.4; 7.25.15.212, 6.1.178, 6.6.145, 6.12.96, 6.18.39, 7.1.4

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: xfs: resample the data fork mapping after cycling ILOCK xfs_reflink_fill_{cow_hole,delalloc} are both presented with an inode, a data fork mapping, and a cow fork mapping. Unfortunately, these two helpers cycle the ILOCK to grab a transaction, which means that the mappings are stale as soon as we reacquire the ILOCK. Currently we refresh the cow fork mapping by re-calling xfs_find_trim_cow_extent, but we don't refresh the data fork mapping beforehand, which means that the xfs_bmap_trim_cow in that function queries the refcount btree about the wrong physical blocks and returns an inaccurate value in *shared. If *shared is now false, the directio write proceeds with a stale data fork mapping. Fix this by querying the data fork mapping if the sequence counter changes across the ILOCK cycle.

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

Technical write-ups (may include proof of concept)

Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities

Spotted an error? Tell us.