Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-64418 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 b9a280a9a454ed514636351d53fe2a233dc5054b, 6465ff3ce65131c774a312d450abe10f4b9f3875, 284c267f013e45d8c89d9fb9373105dc8e6c0947 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 0.1% 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 b9a280a9a454ed514636351d53fe2a233dc5054b or 6465ff3ce65131c774a312d450abe10f4b9f3875 or 284c267f013e45d8c89d9fb9373105dc8e6c0947 or 65476d31d8056e859c48580f82295ce159196ffe, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.96 or 6.18.39 or 7.1.4, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 307bececcd1205bcb67a3c0d53a69db237ccc9d4 up to, but not including, b9a280a9a454ed514636351d53fe2a233dc5054b; 307bececcd1205bcb67a3c0d53a69db237ccc9d4 up to, but not including, 6465ff3ce65131c774a312d450abe10f4b9f3875; 307bececcd1205bcb67a3c0d53a69db237ccc9d4 up to, but not including, 284c267f013e45d8c89d9fb9373105dc8e6c0947; 307bececcd1205bcb67a3c0d53a69db237ccc9d4 up to, but not including, 65476d31d8056e859c48580f82295ce159196ffe; 6.7 | b9a280a9a454ed514636351d53fe2a233dc5054b, 6465ff3ce65131c774a312d450abe10f4b9f3875, 284c267f013e45d8c89d9fb9373105dc8e6c0947, 65476d31d8056e859c48580f82295ce159196ffe |
| Linux | Linux Kernel | 6.7 up to, but not including, 6.12.96; 6.13 up to, but not including, 6.18.39; 6.19 up to, but not including, 7.1.4; 7.2 | 6.12.96, 6.18.39, 7.1.4 |
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: mm: shrinker: fix shrinker_info teardown race with expansion expand_shrinker_info() iterates all visible memcgs under shrinker_mutex, including memcgs that have not finished ->css_online() yet. Once pn->shrinker_info has been published, teardown must stay serialized with expand_shrinker_info() until that memcg is either fully online or no longer visible to iteration. Today alloc_shrinker_info() breaks that rule by dropping shrinker_mutex before freeing a partially initialized shrinker_info array, which may cause the following race: CPU0 CPU1 ==== ==== css_create --> list_add_tail_rcu(&css->sibling, &parent_css->children); online_css --> mem_cgroup_css_online --> alloc_shrinker_info --> alloc node0 info rcu_assign_pointer(C->node0->shrinker_info, old0) alloc node1 info -> FAIL -> goto err mutex_unlock(shrinker_mutex) shrinker_alloc() --> shrinker_memcg_alloc --> mutex_lock(shrinker_mutex) expand_shrinker_info --> mem_cgroup_iter see the memcg expand_one_shrinker_info --> old0 = C->node0->shrinker_info memcpy(new->unit, old0->unit, ...); free_shrinker_info --> kvfree(old0); /* double free !! */ kvfree_rcu(old0, rcu); The same problem exists later in mem_cgroup_css_online(). If alloc_shrinker_info() succeeds but a subsequent objcg allocation fails, the free_objcg -> free_shrinker_info() unwind path tears down the already published pn->shrinker_info arrays without shrinker_mutex. The expand_one_shrinker_info() can race with that teardown in the same way, leading to use-after-free or double-free of the old shrinker_info. Fix this by serializing shrinker_info teardown with shrinker_mutex, and by keeping alloc_shrinker_info() error cleanup inside the locked section.
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.
- 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
- 7.0 High severity
- 7.1 High severity
- 8.2 High severity
- 7.8 High severity
- 7.8 High severity
- 7.8 High severity
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