CyberSecBulletin
CVE-2026-63945NVD status: Analyzed

Linux: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2026-63945 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 d9cbf7144ec589a3f0cc91f74a1a1af2d2b14afa, 35f68f36d9883d56dec21cf85f7556d4657fc393, 996c2104d0726a8fe584f85b3d6327197374a348 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 d9cbf7144ec589a3f0cc91f74a1a1af2d2b14afa or 35f68f36d9883d56dec21cf85f7556d4657fc393 or 996c2104d0726a8fe584f85b3d6327197374a348 or bc08c15746f25f41dd0508b25780d1e84acbb2ef, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 6.1.176 or 6.6.143 or 6.12.93 or 6.18.35, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, d9cbf7144ec589a3f0cc91f74a1a1af2d2b14afa; ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, 35f68f36d9883d56dec21cf85f7556d4657fc393; ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, 996c2104d0726a8fe584f85b3d6327197374a348; ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, bc08c15746f25f41dd0508b25780d1e84acbb2ef; ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, 51cb9dcfdf9a1bccf312ab2ae4b62db629f7dcd5; ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, 4b5f8e608749b7e8fa386c6e4301cf9272595859; 6.0d9cbf7144ec589a3f0cc91f74a1a1af2d2b14afa, 35f68f36d9883d56dec21cf85f7556d4657fc393, 996c2104d0726a8fe584f85b3d6327197374a348, bc08c15746f25f41dd0508b25780d1e84acbb2ef, 51cb9dcfdf9a1bccf312ab2ae4b62db629f7dcd5, 4b5f8e608749b7e8fa386c6e4301cf9272595859
LinuxLinux Kernel6.0 up to, but not including, 6.1.176; 6.2 up to, but not including, 6.6.143; 6.7 up to, but not including, 6.12.93; 6.13 up to, but not including, 6.18.35; 6.19 up to, but not including, 7.0.12; 7.16.1.176, 6.6.143, 6.12.93, 6.18.35, 7.0.12

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: Bluetooth: ISO: serialize iso_sock_clear_timer with socket lock iso_sock_close() calls iso_sock_clear_timer() before acquiring lock_sock(sk). iso_sock_clear_timer() reads iso_pi(sk)->conn twice without the socket lock held: if (!iso_pi(sk)->conn) return; cancel_delayed_work(&iso_pi(sk)->conn->timeout_work); Concurrently, iso_conn_del() executes under lock_sock(sk) and calls iso_chan_del(), which sets iso_pi(sk)->conn to NULL and may result in the final reference to the connection being dropped: CPU0 CPU1 ---- ---- iso_sock_clear_timer() if (conn != NULL) ... lock_sock(sk) iso_chan_del() iso_pi(sk)->conn = NULL cancel_delayed_work(conn) /* NULL deref or UAF */ iso_pi(sk)->conn is not stable across the unlock window, causing a NULL pointer dereference or use-after-free. Serialize iso_sock_clear_timer() with the socket lock by moving it inside lock_sock()/release_sock(), matching the pattern used in iso_conn_del() and all other call sites.

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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