CVE-2025-40266VulnerabilityPublished 4 Dec 2025Updated 30 Jul 2026

CVE-2025-40266: Linux kernel · KVM: arm64: Check the untrusted offset in FF-A memory share Verify the offset to

Source GCVE Database

Not known to be exploited · CVSS 8.2 High.

Data as of 26 Oct 2026, 06:15 UTC

CVSS 3.1 base score

8.2High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 4% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Attack Vector: Local
Attack Complexity: Low
Privileges Required: High
User Interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 2026-10-25.

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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC 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.

ghsa-3fjr-pmvp-g6q5

What to do

AI-suggested

A fix for this vulnerability has been implemented in the Linux kernel. Users and administrators should apply the official kernel updates that include the patch for CVE-2025-40266 to ensure the offset validation is enforced. Since this is a kernel-level vulnerability, updating to a patched kernel version is the recommended remediation. Patch status is not explicitly confirmed in the provided data; therefore, check the official Linux kernel advisories for the exact patched versions and update accordingly.

Description

A high-severity vulnerability in the Linux kernel's KVM arm64 implementation was resolved. The issue involved insufficient verification of an untrusted offset in the FF-A memory share, which could lead to out-of-bounds (OOB) access in the hypervisor. Specifically, if the host kernel set a large enough offset value near the upper limit of a 32-bit unsigned integer range, it could cause memory access beyond intended boundaries. This vulnerability has been addressed by adding proper offset checks to prevent such OOB access.

Impact

If exploited, this vulnerability could allow an attacker with high privileges on the host to cause out-of-bounds memory access in the hypervisor, potentially leading to confidentiality, integrity, and availability compromises of the virtualized environment. The CVSS vector indicates local attack vector with low attack complexity, requiring high privileges and no user interaction, with scope change and high impact on confidentiality, integrity, and availability.

Summary

The Linux kernel's KVM arm64 component had a vulnerability (CVE-2025-40266) where the offset used in FF-A memory sharing was not properly validated. This lack of validation allowed an untrusted offset value, close to U32_MAX, to cause out-of-bounds memory access in the hypervisor. The vulnerability was resolved by implementing checks on the offset to ensure it does not exceed safe bounds, preventing potential memory corruption or escalation of privileges in the hypervisor context.

References

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