CVE-2025-21779

Host kernel crash via unchecked SEND_IPI hypercall

Published Feb 27, 2025 · Updated May 11, 2026

NULL-pointer dereference in affected Linux KVM builds allows guest OS users to crash the host kernel via a Hyper-V SEND_IPI hypercall. kvm_hv_send_ipi passes an interrupt to __apic_accept_irq even when the local APIC is emulated in userspace and no in-kernel APIC exists. The path requires Hyper-V enlightenments with a userspace-emulated local APIC, and successful invocation interrupts the host through a kernel crash.

CVSS severity5.5
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL-pointer dereference in affected Linux KVM builds allows guest OS users to crash the host kernel via a Hyper-V SEND_IPI hypercall. kvm_hv_send_ipi passes an interrupt to __apic_accept_irq even when the local APIC is emulated in userspace and no in-kernel APIC exists. The path requires Hyper-V enlightenments with a userspace-emulated local APIC, and successful invocation interrupts the host through a kernel crash.

The record

CVE
CVE-2025-21779
Published
Feb 27, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-476, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 27, 2025CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=214ff83d4473a7757fa18a64dc7efe3b0e158486 <45fa526b0f5a34492ed0536c3cdf88b78380e4de
  2. Affected versionversion=214ff83d4473a7757fa18a64dc7efe3b0e158486 <5393cf22312418262679eaadb130d608c75fe690
  3. Affected versionversion=214ff83d4473a7757fa18a64dc7efe3b0e158486 <61224533f2b61e252b03e214195d27d64b22989a
  4. Affected versionversion=214ff83d4473a7757fa18a64dc7efe3b0e158486 <874ff13c73c45ecb38cb82191e8c1d523f0dc81b
  5. Affected versionversion=214ff83d4473a7757fa18a64dc7efe3b0e158486 <a8de7f100bb5989d9c3627d3a223ee1c863f3b69
  6. Affected versionversion=214ff83d4473a7757fa18a64dc7efe3b0e158486 <aca8be4403fb90db7adaf63830e27ebe787a76e8
  7. Affected versionversion=214ff83d4473a7757fa18a64dc7efe3b0e158486 <ca29f58ca374c40a0e69c5306fc5c940a0069074
  8. Affected versionversion=4.20

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=214ff83d4473a7757fa18a64dc7efe3b0e158486 <45fa526b0f5a34492ed0536c3cdf88b78380e4de; version=214ff83d4473a7757fa18a64dc7efe3b0e158486 <5393cf22312418262679eaadb130d608c75fe690; version=214ff83d4473a7757fa18a64dc7efe3b0e158486 <61224533f2b61e252b03e214195d27d64b22989a; version=214ff83d4473a7757fa18a64dc7efe3b0e158486 <874ff13c73c45ecb38cb82191e8c1d523f0dc81b; version=214ff83d4473a7757fa18a64dc7efe3b0e158486 <a8de7f100bb5989d9c3627d3a223ee1c863f3b69; version=214ff83d4473a7757fa18a64dc7efe3b0e158486 <aca8be4403fb90db7adaf63830e27ebe787a76e8; version=214ff83d4473a7757fa18a64dc7efe3b0e158486 <ca29f58ca374c40a0e69c5306fc5c940a0069074; version=4.20

Published CVSS scores

5.5NIST National Vulnerability DatabaseCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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