CyberSecBulletin
CVE-2026-64206NVD status: Modified

Linux: Concurrent Execution using Shared Resource with Improper Synchronization

Published Updated By the CyberSecBulletin desk

CVE-2026-64206 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 from the same local network by an unauthenticated attacker, without any action from a user. The record lists versions fc0c3b9cf27cfa2a06f66dae1d08c668fe0a2faa, 9901f847a762a5d953871dd95767ce2aed3d684d, 4a0bb0fd63fe2b0c62e1072cd1811d6f61e0081c 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 0.25% 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 fc0c3b9cf27cfa2a06f66dae1d08c668fe0a2faa or 9901f847a762a5d953871dd95767ce2aed3d684d or 4a0bb0fd63fe2b0c62e1072cd1811d6f61e0081c or 8daaf7f73fe998631a160d1a5a7e1b0b0480eef8, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 3.16 or 5.10.261 or 5.15.212 or 6.1.178, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux7ab56c3a6eccb215034b0cb096e0313441cbf2a4 up to, but not including, fc0c3b9cf27cfa2a06f66dae1d08c668fe0a2faa; 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 up to, but not including, 9901f847a762a5d953871dd95767ce2aed3d684d; 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 up to, but not including, 4a0bb0fd63fe2b0c62e1072cd1811d6f61e0081c; 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 up to, but not including, 8daaf7f73fe998631a160d1a5a7e1b0b0480eef8; 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 up to, but not including, 8de7b386ffad480ca59222b688c94a2da8f0d805; 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 up to, but not including, d5616beb3355b5fca2280d796c1cf7ada4ee6551; 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 up to, but not including, e96fbac8d3a73b0bc165383c092a30628561d320; 7ab56c3a6eccb215034b0cb096e0313441cbf2a4 up to, but not including, 2641a9e0a1dd4af2e21995470a21d55dd35e5203; and 3 more rangesfc0c3b9cf27cfa2a06f66dae1d08c668fe0a2faa, 9901f847a762a5d953871dd95767ce2aed3d684d, 4a0bb0fd63fe2b0c62e1072cd1811d6f61e0081c, 8daaf7f73fe998631a160d1a5a7e1b0b0480eef8, 8de7b386ffad480ca59222b688c94a2da8f0d805, d5616beb3355b5fca2280d796c1cf7ada4ee6551
LinuxLinux Kernel3.15.5 up to, but not including, 3.16; 3.16.1 up to, but not including, 5.10.261; 5.11 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, 6.12.97; 6.13 up to, but not including, 6.18.39; 6.19 up to, but not including, 7.1.4; and 2 more ranges3.16, 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97

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
AdjacentThe attacker must be on the same local network segment.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
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:A/AC:L/PR:N/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: L2CAP: cancel pending_rx_work before taking conn->lock l2cap_conn_del() takes conn->lock and then calls cancel_work_sync() for pending_rx_work. process_pending_rx() takes the same mutex, so teardown can deadlock against the worker it is flushing. This issue was found by our static analysis tool and then manually reviewed against the current tree. The grounded PoC kept the l2cap_conn_ready() -> queue_work(..., &conn->pending_rx_work) submit path, the l2cap_conn_del() -> cancel_work_sync(&conn->pending_rx_work) teardown path, and the process_pending_rx() -> mutex_lock(&conn->lock) worker edge. Lockdep WARNING: possible circular locking dependency detected process_pending_rx+0x21/0x2a [vuln_msv] l2cap_conn_del.constprop.0+0x3f/0x4e [vuln_msv] *** DEADLOCK *** Cancel pending_rx_work before taking conn->lock, matching the existing lock-before-drain ordering used for the two delayed works in the same teardown path. The pending_rx queue is still purged after the work has been cancelled and conn->lock has been acquired.

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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