Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-31539 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions e811e60e1cc79923c4388146eb1fa26a7482731e, f99996870222b598914a1f49d7375dc23752c237, 6e3c5052f9686192e178806e017b7377155f4bab 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 0.33% 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 e811e60e1cc79923c4388146eb1fa26a7482731e or f99996870222b598914a1f49d7375dc23752c237 or 6e3c5052f9686192e178806e017b7377155f4bab, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.18.11 or 6.19.1, whichever matches your release line, or a later version.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 5fb9b459b3686e366640edd4e62805ef7b4de927 up to, but not including, e811e60e1cc79923c4388146eb1fa26a7482731e; 5fb9b459b3686e366640edd4e62805ef7b4de927 up to, but not including, f99996870222b598914a1f49d7375dc23752c237; 5fb9b459b3686e366640edd4e62805ef7b4de927 up to, but not including, 6e3c5052f9686192e178806e017b7377155f4bab; 6.18 | e811e60e1cc79923c4388146eb1fa26a7482731e, f99996870222b598914a1f49d7375dc23752c237, 6e3c5052f9686192e178806e017b7377155f4bab |
| Linux | Linux Kernel | 6.18 up to, but not including, 6.18.11; 6.19 up to, but not including, 6.19.1 | 6.18.11, 6.19.1 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- 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
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: smb: smbdirect: introduce smbdirect_socket.recv_io.credits.available The logic off managing recv credits by counting posted recv_io and granted credits is racy. That's because the peer might already consumed a credit, but between receiving the incoming recv at the hardware and processing the completion in the 'recv_done' functions we likely have a window where we grant credits, which don't really exist. So we better have a decicated counter for the available credits, which will be incremented when we posted new recv buffers and drained when we grant the credits to the peer.
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: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 7.8 High severity
- 8.3 High severity
- 7.8 High severity
- 7.8 High severity
- 8.2 High severity
- 8.7 High severity
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