CVE-2025-21976

Local kernel compromise via stale framebuffer mapping

Published Apr 1, 2025 · Updated Aug 5, 2026

Use-after-free in the Linux kernel hyperv_fb driver allows local users to read or write kernel memory through a stale framebuffer mapping. The hvfb_remove function prematurely frees framebuffer storage while an open mmap and the info->pagerefs array still reference recycled pages. Access requires permission to map /dev/fbN and a device-removal event while that mapping remains open; subsequent access can corrupt memory or panic the kernel.

CVSS severity7.8
High
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the Linux kernel hyperv_fb driver allows local users to read or write kernel memory through a stale framebuffer mapping. The hvfb_remove function prematurely frees framebuffer storage while an open mmap and the info->pagerefs array still reference recycled pages. Access requires permission to map /dev/fbN and a device-removal event while that mapping remains open; subsequent access can corrupt memory or panic the kernel.

The record

CVE
CVE-2025-21976
Published
Apr 1, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=3.10
  2. Affected versionversion=68a2d20b79b105f02dcbc52c211d7e62f98996b7 <4545e2aa121aea304d33903099c03e29ed4fe50a
  3. Affected versionversion=68a2d20b79b105f02dcbc52c211d7e62f98996b7 <a7b583dc99c6cf4a96877017be1d08247e1ef2c7
  4. Affected versionversion=68a2d20b79b105f02dcbc52c211d7e62f98996b7 <ea2f45ab0e53b255f72c85ccd99e2b394fc5fceb

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=3.10; version=68a2d20b79b105f02dcbc52c211d7e62f98996b7 <4545e2aa121aea304d33903099c03e29ed4fe50a; version=68a2d20b79b105f02dcbc52c211d7e62f98996b7 <a7b583dc99c6cf4a96877017be1d08247e1ef2c7; version=68a2d20b79b105f02dcbc52c211d7e62f98996b7 <ea2f45ab0e53b255f72c85ccd99e2b394fc5fceb

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
7.8Linux kernel CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1068Exploitation for Privilege Escalation

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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