Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-45894 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 bed36f5657d34ae982d48045a75bff6113790cf9, c36b0515c6445bd137ec8ad86ef5470c45d6e4bf, a84d30e8d2bacd21782a6481158b7c9c552f4868 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 bed36f5657d34ae982d48045a75bff6113790cf9 or c36b0515c6445bd137ec8ad86ef5470c45d6e4bf or a84d30e8d2bacd21782a6481158b7c9c552f4868 or 821807c167b7b48a41b95b6607c6b9f97600f7d9, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.12.75 or 6.18.14 or 6.19.4, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 up to, but not including, bed36f5657d34ae982d48045a75bff6113790cf9; 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 up to, but not including, c36b0515c6445bd137ec8ad86ef5470c45d6e4bf; 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 up to, but not including, a84d30e8d2bacd21782a6481158b7c9c552f4868; 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 up to, but not including, 821807c167b7b48a41b95b6607c6b9f97600f7d9; 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 up to, but not including, 949d71666e9dd19f21e7b4b53a88cd2c5b902858; 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 up to, but not including, 75ed00055c059dedc47b5daaaa2f8a7a019138ff; 5.0 | bed36f5657d34ae982d48045a75bff6113790cf9, c36b0515c6445bd137ec8ad86ef5470c45d6e4bf, a84d30e8d2bacd21782a6481158b7c9c552f4868, 821807c167b7b48a41b95b6607c6b9f97600f7d9, 949d71666e9dd19f21e7b4b53a88cd2c5b902858, 75ed00055c059dedc47b5daaaa2f8a7a019138ff |
| Linux | Linux Kernel | 5.0 up to, but not including, 6.12.75; 6.13 up to, but not including, 6.18.14; 6.19 up to, but not including, 6.19.4 | 6.12.75, 6.18.14, 6.19.4 |
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
- HighSuccess depends on conditions outside the attacker's control.
- 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:H/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: iommu/vt-d: Clear Present bit before tearing down PASID entry The Intel VT-d Scalable Mode PASID table entry consists of 512 bits (64 bytes). When tearing down an entry, the current implementation zeros the entire 64-byte structure immediately using multiple 64-bit writes. Since the IOMMU hardware may fetch these 64 bytes using multiple internal transactions (e.g., four 128-bit bursts), updating or zeroing the entire entry while it is active (P=1) risks a "torn" read. If a hardware fetch occurs simultaneously with the CPU zeroing the entry, the hardware could observe an inconsistent state, leading to unpredictable behavior or spurious faults. Follow the "Guidance to Software for Invalidations" in the VT-d spec (Section 6.5.3.3) by implementing the recommended ownership handshake: 1. Clear only the 'Present' (P) bit of the PASID entry. 2. Use a dma_wmb() to ensure the cleared bit is visible to hardware before proceeding. 3. Execute the required invalidation sequence (PASID cache, IOTLB, and Device-TLB flush) to ensure the hardware has released all cached references. 4. Only after the flushes are complete, zero out the remaining fields of the PASID entry. Also, add a dma_wmb() in pasid_set_present() to ensure that all other fields of the PASID entry are visible to the hardware before the Present bit is set.
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
Other references
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