Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-63946 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 c57ea90f203c8b8b41a474f19a09000d0f841436, 119fb6f80c44dc1c65d604cf28e64c56bd9b6568, b04ec131325baf4ea4577d6c6e6b86cf092e3731 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 0.26% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to c57ea90f203c8b8b41a474f19a09000d0f841436 or 119fb6f80c44dc1c65d604cf28e64c56bd9b6568 or b04ec131325baf4ea4577d6c6e6b86cf092e3731 or c318aa51830a3d2cc1229968fe521441c97356cd, whichever matches your release line, or a later version.
- 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
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, c57ea90f203c8b8b41a474f19a09000d0f841436; ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, 119fb6f80c44dc1c65d604cf28e64c56bd9b6568; ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, b04ec131325baf4ea4577d6c6e6b86cf092e3731; ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, c318aa51830a3d2cc1229968fe521441c97356cd; ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, 1a6b803b00ccdd7666506adbe01ddae1c72d1ca9; ccf74f2390d60a2f9a75ef496d2564abb478f46a up to, but not including, 47f23a259517abbdb8032c057a1e8a6bf3734878; 6.0 | c57ea90f203c8b8b41a474f19a09000d0f841436, 119fb6f80c44dc1c65d604cf28e64c56bd9b6568, b04ec131325baf4ea4577d6c6e6b86cf092e3731, c318aa51830a3d2cc1229968fe521441c97356cd, 1a6b803b00ccdd7666506adbe01ddae1c72d1ca9, 47f23a259517abbdb8032c057a1e8a6bf3734878 |
| Linux | Linux Kernel | 6.0 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; 7.1 | 6.1.176, 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
- 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: ISO: fix UAF in iso_recv_frame iso_recv_frame reads conn->sk under iso_conn_lock but releases the lock before using sk, with no reference held. A concurrent iso_sock_kill() can free sk in that window, causing use-after-free on sk->sk_state and sock_queue_rcv_skb(). Fix by replacing the bare pointer read with iso_sock_hold(conn), which calls sock_hold() while the spinlock is held, atomically elevating the refcount before the lock drops. Add a drop_put label so sock_put() is called on all exit paths where the hold succeeded.
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).
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/119fb6f80c44dc1c65d604cf28e64c56bd9b6568
- git.kernel.org/stable/c/1a6b803b00ccdd7666506adbe01ddae1c72d1ca9
- git.kernel.org/stable/c/47f23a259517abbdb8032c057a1e8a6bf3734878
- git.kernel.org/stable/c/b04ec131325baf4ea4577d6c6e6b86cf092e3731
- git.kernel.org/stable/c/c318aa51830a3d2cc1229968fe521441c97356cd
- git.kernel.org/stable/c/c57ea90f203c8b8b41a474f19a09000d0f841436
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 9.8 Critical severity
- 9.8 Critical severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
Spotted an error? Tell us.