SB2026100958 - Out-of-bounds read in Linux kernel __vlan_insert_inner_tag() in include/linux/if_vlan.h

Description

This security bulletin contains information about 1 vulnerability.

1) Out-of-bounds read (CVE-ID: CVE-2026-98377)

CWE-ID: CWE-125 - Out-of-bounds read

CVSSv4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]

The vulnerability allows a local user to disclose uninitialized kernel slab memory.

The vulnerability exists due to an out-of-bounds read caused by insufficient verification of MAC header availability in __vlan_insert_inner_tag() when inserting VLAN tags into undersized frames. A local user can send a one-byte AF_PACKET/SOCK_RAW frame through an IFF_TUN device subjected to repeated VLAN pushes to disclose uninitialized kernel slab memory.

The IFF_TUN device has hard_header_len set to zero. The first VLAN push sets only a hardware-accelerated tag; subsequent pushes reach the helper through a clsact VLAN push action or bpf_skb_vlan_push().

Remediation

Install update from vendor's website.

References

• https://git.kernel.org/stable/c/40a5cc4b7251c74f3341332a226d02200e96bccf
• https://git.kernel.org/stable/c/59af43ccece4d2d8b62e9e3ccc96b6e2e793bcdc
• https://git.kernel.org/stable/c/ab888242fce4f16f6c4d4c6ec53939ad36aa3b3a
• https://git.kernel.org/stable/c/f42562dd027dc4ed103fae17b2206e73ea1963c4