CVE-2025-21920Public exploit

Kernel-address disclosure via VLAN out-of-bounds read

Published Apr 1, 2025 · Updated May 11, 2026

An out-of-bounds read in the Linux VLAN subsystem allows local users to disclose a kernel function address via a crafted VLAN. VLAN creation runs GARP and MRP initialization on a non-Ethernet lower device, causing __dev_mc_add to read dev->addr_len bytes from a six-byte multicast address. The documented trigger requires permission to create tunnel and VLAN interfaces, and the demonstrated consequence is disclosure of one kernel code address.

CVSS severity7.1
High
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

An out-of-bounds read in the Linux VLAN subsystem allows local users to disclose a kernel function address via a crafted VLAN. VLAN creation runs GARP and MRP initialization on a non-Ethernet lower device, causing __dev_mc_add to read dev->addr_len bytes from a six-byte multicast address. The documented trigger requires permission to create tunnel and VLAN interfaces, and the demonstrated consequence is disclosure of one kernel code address.

The record

CVE
CVE-2025-21920
Published
Apr 1, 2025
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 1, 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=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <0fb7aa04c19eac4417f360a9f7611a60637bdacc
  2. Affected versionversion=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <30e8aee77899173a82ae5ed89f536c096f20aaeb
  3. Affected versionversion=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <3561442599804905c3defca241787cd4546e99a7
  4. Affected versionversion=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <5a515d13e15536e82c5c7c83eb6cf5bc4827fee5
  5. Affected versionversion=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <7f1564b2b2072b7aa1ac75350e9560a07c7a44fd
  6. Affected versionversion=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <b33a534610067ade2bdaf2052900aaad99701353
  7. Affected versionversion=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <b6c72479748b7ea09f53ed64b223cee6463dc278
  8. Affected versionversion=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <fa40ebef69234e39ec2d26930d045f2fb9a8cb2b
  9. Affected versionversion=2.6.35

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <0fb7aa04c19eac4417f360a9f7611a60637bdacc; version=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <30e8aee77899173a82ae5ed89f536c096f20aaeb; version=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <3561442599804905c3defca241787cd4546e99a7; version=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <5a515d13e15536e82c5c7c83eb6cf5bc4827fee5; version=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <7f1564b2b2072b7aa1ac75350e9560a07c7a44fd; version=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <b33a534610067ade2bdaf2052900aaad99701353; version=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <b6c72479748b7ea09f53ed64b223cee6463dc278; version=22bedad3ce112d5ca1eaf043d4990fa2ed698c87 <fa40ebef69234e39ec2d26930d045f2fb9a8cb2b; version=2.6.35

Published CVSS scores

7.1NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
7.1Amazon LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/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.

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 exploitPublished

Weakness, pattern, technique

CWE-125Out-of-bounds Read

Public exploit references

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo