Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-45944 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 with local access to the system by an attacker with administrator privileges, without any action from a user. The record lists versions 61fa8546e39331103d6ce01575699c577d83e000, ab4aeab2d630e68be60ccbea3fcf76fa7c281a18, c716a59e9977d751e5eb54bcfa6a80124cb5067b 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 0.12% 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 61fa8546e39331103d6ce01575699c577d83e000 or ab4aeab2d630e68be60ccbea3fcf76fa7c281a18 or c716a59e9977d751e5eb54bcfa6a80124cb5067b or d2138abc8f0a7fce4101b7229b43b06811ed083d, whichever matches your release line, or a later version.
- Update Linux Kernel to 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 | ba39592764ed20cee09aae5352e603a27bf56b0d up to, but not including, 61fa8546e39331103d6ce01575699c577d83e000; ba39592764ed20cee09aae5352e603a27bf56b0d up to, but not including, ab4aeab2d630e68be60ccbea3fcf76fa7c281a18; ba39592764ed20cee09aae5352e603a27bf56b0d up to, but not including, c716a59e9977d751e5eb54bcfa6a80124cb5067b; ba39592764ed20cee09aae5352e603a27bf56b0d up to, but not including, d2138abc8f0a7fce4101b7229b43b06811ed083d; ba39592764ed20cee09aae5352e603a27bf56b0d up to, but not including, a922dbafb4a674d958d702038232d09a30daf770; ba39592764ed20cee09aae5352e603a27bf56b0d up to, but not including, c1e4f1dccbe9d7656d1c6872ebeadb5992d0aaa2; 2.6.24 | 61fa8546e39331103d6ce01575699c577d83e000, ab4aeab2d630e68be60ccbea3fcf76fa7c281a18, c716a59e9977d751e5eb54bcfa6a80124cb5067b, d2138abc8f0a7fce4101b7229b43b06811ed083d, a922dbafb4a674d958d702038232d09a30daf770, c1e4f1dccbe9d7656d1c6872ebeadb5992d0aaa2 |
| Linux | Linux Kernel | 2.6.24 up to, but not including, 6.18.14; 6.19 up to, but not including, 6.19.4 | 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
- HighAdministrator-level access is required first.
- 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:H/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 context entry When tearing down a context entry, the current implementation zeros the entire 128-bit entry using multiple 64-bit writes. This creates a window where the hardware can fetch a "torn" entry — where some fields are already zeroed while the 'Present' bit is still set — leading to unpredictable behavior or spurious faults. While x86 provides strong write ordering, the compiler may reorder writes to the two 64-bit halves of the context entry. Even without compiler reordering, the hardware fetch is not guaranteed to be atomic with respect to multiple CPU writes. Align with 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 context entry first to signal the transition of ownership from hardware to software. 2. Use dma_wmb() to ensure the cleared bit is visible to the IOMMU. 3. Perform the required cache and context-cache invalidation to ensure hardware no longer has cached references to the entry. 4. Fully zero out the entry only after the invalidation is complete. Also, add a dma_wmb() to context_set_present() to ensure the entry is fully initialized before the 'Present' bit becomes visible.
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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