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CVE-2025-21920

vlan: enforce underlying device type PUBLISHED

Description (CNA)

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.

Affected (CNA)

Vendor / productVersions
Linux / Linuxaffected 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 before 7f1564b2b2072b7aa1ac75350e9560a07c7a44fd; affected 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 before fa40ebef69234e39ec2d26930d045f2fb9a8cb2b; affected 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 before 0fb7aa04c19eac4417f360a9f7611a60637bdacc; affected 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 before 5a515d13e15536e82c5c7c83eb6cf5bc4827fee5; affected 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 before 3561442599804905c3defca241787cd4546e99a7; affected 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 before 30e8aee77899173a82ae5ed89f536c096f20aaeb; affected 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 before b6c72479748b7ea09f53ed64b223cee6463dc278; affected 22bedad3ce112d5ca1eaf043d4990fa2ed698c87 before b33a534610067ade2bdaf2052900aaad99701353
Linux / Linuxaffected 2.6.35; unaffected 0 before 2.6.35; unaffected 5.4.291 through 5.4.*; unaffected 5.10.235 through 5.10.*; unaffected 5.15.179 through 5.15.*; unaffected 6.1.131 through 6.1.*; unaffected 6.6.83 through 6.6.*; unaffected 6.12.19 through 6.12.*; unaffected 6.13.7 through 6.13.*; unaffected 6.14 through *

CWE

No CWE identifiers supplied.

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.

CVE

No English description supplied.