CVE-2025-40274VulnerabilityPublished 7 Dec 2025Updated 30 Jul 2026

CVE-2025-40274: Linux kernel · KVM: guest_memfd: Remove bindings on memslot deletion when gmem is dying When

Source GCVE Database

Not known to be exploited · CVSS 7.8 High.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

7.8High

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 3% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
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 7 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 2026-10-26.

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-h3qw-rx4w-h8fj

What to do

AI-suggested

Since no explicit patch or official fix link is provided, users should monitor Linux kernel updates and apply relevant patches once available. Until then, avoid untrusted manipulation of KVM guest memory regions involving guest_memfd. No vendor advisory states 'no action required' or 'already mitigated'.

Description

A use-after-free vulnerability in the Linux kernel's KVM guest_memfd component was resolved. The issue occurs when unbinding a memslot from a guest_memfd instance while the guest_memfd file is in the process of being released, leading to a write operation on freed memory. This was detected by KASAN as a slab-use-after-free bug. The vulnerability could allow an attacker with local privileges to cause memory corruption with high impact on confidentiality, integrity, and availability.

Impact

This vulnerability allows local attackers with the ability to manipulate KVM guest memory regions to trigger a use-after-free condition, potentially leading to memory corruption. The CVSS vector indicates high impact on confidentiality, integrity, and availability. Exploitation could result in privilege escalation or denial of service within the affected Linux kernel environment.

Summary

The vulnerability (CVE-2025-40274) in the Linux kernel's KVM subsystem involves improper handling of memslot bindings during memslot deletion when the guest_memfd file reference count has dropped to zero (file is dying). Specifically, the bindings were not removed correctly, causing kvm_gmem_release() to write to freed memory, resulting in a use-after-free condition. This was identified by KASAN instrumentation. The root cause is that the lifecycle of the file mapping is outside KVM's control, and the code did not properly handle the memslot unbinding in this edge case. The fix involves removing bindings even if the guest_memfd file is dying to prevent use-after-free.

References

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