Host data disclosure via guest-poisoned branch predictions
Published Sep 11, 2025 · Updated Sep 8, 2026
Information disclosure in Linux x86 KVM allows guest OS users to read host userspace data through poisoned branch predictions. After a VM exit, the kernel can return directly to a userspace hypervisor without issuing an Indirect Branch Prediction Barrier, allowing guest-influenced predictor state to steer speculative execution in that hypervisor. Exploitation requires code execution in a guest on an affected Intel, AMD, or Hygon processor; the reported consequence is host-userspace data exposure, not kernel compromise.
Summary
What happened
Information disclosure in Linux x86 KVM allows guest OS users to read host userspace data through poisoned branch predictions. After a VM exit, the kernel can return directly to a userspace hypervisor without issuing an Indirect Branch Prediction Barrier, allowing guest-influenced predictor state to steer speculative execution in that hypervisor. Exploitation requires code execution in a guest on an affected Intel, AMD, or Hygon processor; the reported consequence is host-userspace data exposure, not kernel compromise.
The record
- CVE
- CVE-2025-40300
- Published
- Sep 11, 2025
- Updated
- Sep 8, 2026
- Vendor
- Siemens
- Product
- SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
- Classifications
- CWE-1341
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 11, 2025CVE publishedPublication date reported by the CVE source.
- Sep 8, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=V3.1.6 <*
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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