CVE-2025-40026VulnerabilityPublished 8 Oct 2026Updated 30 Oct 2026

Red Hat Security Advisory: kernel security update

Affects Linux kernelSource GCVE Database

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Not known to be exploited.

Data as of 30 Oct 2026, 11:52 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
CVE published 8 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

AI-suggested

A security update for the kernel is available from Red Hat for Red Hat Enterprise Linux 7 Extended Lifecycle Support. Users should apply the update as described in Red Hat's advisory and reboot their systems to ensure the fix is active. Red Hat strongly recommends not delaying the update to avoid exposure. Treat all kernel errata as security-relevant and apply patches promptly.

Description

A moderate severity security vulnerability (CVE-2025-40026) exists in the Linux kernel's KVM x86 component related to improper (re)checking of L1 intercepts during userspace I/O completion. This issue affects Red Hat Enterprise Linux 7 Extended Lifecycle Support kernel packages. A security update is available and should be applied, requiring a system reboot for the fix to take effect. Red Hat recommends treating all kernel errata as security-relevant due to the kernel's critical role in system security.

Impact

The vulnerability affects the kernel's KVM x86 virtualization code, which could lead to security issues related to userspace I/O operations. The impact is rated moderate by Red Hat. No known exploits in the wild have been reported. Given the kernel's fundamental role, any flaw may have broader security implications, but specific exploitation details are not provided.

Summary

The vulnerability CVE-2025-40026 involves the Linux kernel's KVM x86 virtualization component, where the kernel improperly (re)checks L1 intercepts when completing userspace I/O operations. This flaw could potentially impact system security. Red Hat has released a security advisory (RHSA-2026:78844) addressing this issue with updated kernel packages for Red Hat Enterprise Linux 7 Extended Lifecycle Support. The advisory rates the update as having a moderate security impact and advises prompt application of the update followed by a system reboot. The kernel update fixes the issue by correcting the handling of L1 intercept checks in the KVM x86 code path.

CWE-754Improper Check for Unusual or Exceptional Conditions (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation
Check the results of all functions that return a value and verify that the value is expected.
Implementation
If using exception handling, catch and throw specific exceptions instead of overly-general exceptions (CWE-396, CWE-397). Catch and handle exceptions as locally as possible so that exceptions do not propagate too far up the call stack (CWE-705). Avoid unchecked or uncaught exceptions where feasible (CWE-248).
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 30 Oct 2026, 10:32 UTC

WeaknessesCWE-754

Technical details

References

Community reviews

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