CVE-2025-21920 | THREATINT

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.

PUBLISHED Reserved 2024-12-29 | Published 2025-04-01 | Updated 2025-11-03 | Assigner Linux

Product status

Default status

unaffected

22bedad3ce112d5ca1eaf043d4990fa2ed698c87 (git) before 7f1564b2b2072b7aa1ac75350e9560a07c7a44fd

affected

22bedad3ce112d5ca1eaf043d4990fa2ed698c87 (git) before fa40ebef69234e39ec2d26930d045f2fb9a8cb2b

affected

22bedad3ce112d5ca1eaf043d4990fa2ed698c87 (git) before 0fb7aa04c19eac4417f360a9f7611a60637bdacc

affected

22bedad3ce112d5ca1eaf043d4990fa2ed698c87 (git) before 5a515d13e15536e82c5c7c83eb6cf5bc4827fee5

affected

22bedad3ce112d5ca1eaf043d4990fa2ed698c87 (git) before 3561442599804905c3defca241787cd4546e99a7

affected

22bedad3ce112d5ca1eaf043d4990fa2ed698c87 (git) before 30e8aee77899173a82ae5ed89f536c096f20aaeb

affected

22bedad3ce112d5ca1eaf043d4990fa2ed698c87 (git) before b6c72479748b7ea09f53ed64b223cee6463dc278

affected

22bedad3ce112d5ca1eaf043d4990fa2ed698c87 (git) before b33a534610067ade2bdaf2052900aaad99701353

affected

Default status

affected

2.6.35

affected

Any version before 2.6.35

unaffected

5.4.291 (semver)

unaffected

5.10.235 (semver)

unaffected

5.15.179 (semver)

unaffected

6.1.131 (semver)

unaffected

6.6.83 (semver)

unaffected

6.12.19 (semver)

unaffected

6.13.7 (semver)

unaffected

6.14 (original_commit_for_fix)

unaffected

References

lists.debian.org/debian-lts-announce/2025/05/msg00045.html

lists.debian.org/debian-lts-announce/2025/05/msg00030.html

git.kernel.org/...c/7f1564b2b2072b7aa1ac75350e9560a07c7a44fd

git.kernel.org/...c/fa40ebef69234e39ec2d26930d045f2fb9a8cb2b

git.kernel.org/...c/0fb7aa04c19eac4417f360a9f7611a60637bdacc

git.kernel.org/...c/5a515d13e15536e82c5c7c83eb6cf5bc4827fee5

git.kernel.org/...c/3561442599804905c3defca241787cd4546e99a7

git.kernel.org/...c/30e8aee77899173a82ae5ed89f536c096f20aaeb

git.kernel.org/...c/b6c72479748b7ea09f53ed64b223cee6463dc278

git.kernel.org/...c/b33a534610067ade2bdaf2052900aaad99701353

cve.org (CVE-2025-21920)

nvd.nist.gov (CVE-2025-21920)

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