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National Vulnerability Database

National Vulnerability Database

NVD

National Vulnerability Database
  1. Vulnerabilities

CVE-2025-21920 Detail

Description

In the Linux kernel, the following vulnerability has been resolved: vlan: enforce underlying device type Currently, VLAN devices can be created on top of non-ethernet devices. Besides the fact that it doesn't make much sense, this also causes a bug which leaks the address of a kernel function to usermode. When creating a VLAN device, we initialize GARP (garp_init_applicant) and MRP (mrp_init_applicant) for the underlying device. As part of the initialization process, we add the multicast address of each applicant to the underlying device, by calling dev_mc_add. __dev_mc_add uses dev->addr_len to determine the length of the new multicast address. This causes an out-of-bounds read if dev->addr_len is greater than 6, since the multicast addresses provided by GARP and MRP are only 6 bytes long. This behaviour can be reproduced using the following commands: ip tunnel add gretest mode ip6gre local ::1 remote ::2 dev lo ip l set up dev gretest ip link add link gretest name vlantest type vlan id 100 Then, the following command will display the address of garp_pdu_rcv: ip maddr show | grep 01:80:c2:00:00:21 Fix the bug by enforcing the type of the underlying device during VLAN device initialization.


Metrics

 
NVD enrichment efforts reference publicly available information to associate vector strings. CVSS information contributed by other sources is also displayed.
CVSS 4.0 Severity and Vector Strings:

NIST CVSS score
NIST: NVD
N/A
NVD assessment not yet provided.

References to Advisories, Solutions, and Tools

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URL Source(s) Tag(s)
https://git.kernel.org/stable/c/0fb7aa04c19eac4417f360a9f7611a60637bdacc kernel.org Patch 
https://git.kernel.org/stable/c/30e8aee77899173a82ae5ed89f536c096f20aaeb kernel.org Patch 
https://git.kernel.org/stable/c/3561442599804905c3defca241787cd4546e99a7 kernel.org Patch 
https://git.kernel.org/stable/c/5a515d13e15536e82c5c7c83eb6cf5bc4827fee5 kernel.org Patch 
https://git.kernel.org/stable/c/7f1564b2b2072b7aa1ac75350e9560a07c7a44fd kernel.org Patch 
https://git.kernel.org/stable/c/b33a534610067ade2bdaf2052900aaad99701353 kernel.org Patch 
https://git.kernel.org/stable/c/b6c72479748b7ea09f53ed64b223cee6463dc278 kernel.org Patch 
https://git.kernel.org/stable/c/fa40ebef69234e39ec2d26930d045f2fb9a8cb2b kernel.org Patch 
https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html CVE
https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html CVE

Weakness Enumeration

CWE-ID CWE Name Source
CWE-125 Out-of-bounds Read cwe source acceptance level NIST   CISA-ADP  

Known Affected Software Configurations Switch to CPE 2.2

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Change History

4 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2025-21920
NVD Published Date:
04/01/2025
NVD Last Modified:
11/03/2025
Source:
kernel.org