Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-63885 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 with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 0dfa42cfe4dbe114533480503934f43e33c1e83d, cde2c9257cbe8463b9dcf7b1075177b72b5fd938, 7164d78559b0ff29931a366a840a9e5dd53d4b7c 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.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 0dfa42cfe4dbe114533480503934f43e33c1e83d or cde2c9257cbe8463b9dcf7b1075177b72b5fd938 or 7164d78559b0ff29931a366a840a9e5dd53d4b7c or 6.18.35, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.18.35 or 7.0.12, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 672464dd53231509c9c771110798c56d4660e19e up to, but not including, 0dfa42cfe4dbe114533480503934f43e33c1e83d; 61bd96d3e5472c253f9c1ab77608f0c8aaa9d025 up to, but not including, cde2c9257cbe8463b9dcf7b1075177b72b5fd938; 5e28b7b94408897e41c63477aabc9e1db439bc8c up to, but not including, 7164d78559b0ff29931a366a840a9e5dd53d4b7c; 6.18.32 up to, but not including, 6.18.35; 7.0.9 up to, but not including, 7.0.12 | 0dfa42cfe4dbe114533480503934f43e33c1e83d, cde2c9257cbe8463b9dcf7b1075177b72b5fd938, 7164d78559b0ff29931a366a840a9e5dd53d4b7c, 6.18.35, 7.0.12 |
| Linux | Linux Kernel | 6.18.32 up to, but not including, 6.18.35; 7.0.9 up to, but not including, 7.0.12; 7.1 | 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
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- 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:C/C:H/I:H/A:H. Scored by CNA.
Official description
In the Linux kernel, the following vulnerability has been resolved: drm/gem: fix race between change_handle and handle_delete drm_gem_change_handle_ioctl leaves the old handle live in the IDR during the window between spin_unlock(table_lock) and the final spin_lock(table_lock). A concurrent drm_gem_handle_delete on the old handle succeeds in this window, decrements handle_count to 0, and frees the GEM object while the new handle's IDR entry still references it. NULL the old handle's IDR entry before dropping table_lock so that any concurrent GEM_CLOSE on the old handle sees NULL and returns -EINVAL. Restore the old entry on the prime-bookkeeping error path.
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
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
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