CVE-2026-81000

Summary

In the Linux kernel, the following vulnerability has been resolved:

net: tun: bound receive headroom

tun_get_user() uses tun->align both as skb headroom and when choosing how much packet data to keep linear. OVS can propagate an oversized headroom request from another port to TUN or TAP.

When align is larger than the usable space in a one-page skb head, SKB_MAX_HEAD(align) underflows and the result becomes negative when stored in good_linear. That value later wraps when assigned to the size_t linear variable, and tun_alloc_skb() can place skb->data outside the allocated head.

Bound the headroom stored by TUN to the one-page skb-head budget and the largest non-sentinel 16-bit skb header offset. Leave one linear byte for raw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN.

Also pull the raw-TUN protocol byte and the TAP Ethernet header before accessing them, so these checks remain safe for nonlinear skbs supplied by other allocation paths.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxeaea34b23c46bf17b4a5638be69ab3561854f34b < 379d85c7f25f3e05a428225e6b8a65613c6e9b9daffected
LinuxLinuxeaea34b23c46bf17b4a5638be69ab3561854f34b < e098d9cc8859614a7f7baebc96e32a5a16b18ed2affected
LinuxLinuxeaea34b23c46bf17b4a5638be69ab3561854f34b < 0ada54ea63e48b9c1608e917ccb7dfadbe86db28affected
LinuxLinuxeaea34b23c46bf17b4a5638be69ab3561854f34b < 447c9303942c439a117d9b76ce6d6e2116b38ee7affected
LinuxLinux4.6affected
LinuxLinux0 < 4.6unaffected
LinuxLinux6.12.109 <= 6.12.*unaffected
LinuxLinux6.18.50 <= 6.18.*unaffected
LinuxLinux7.2.4 <= 7.2.*unaffected
LinuxLinux7.3-rc1 <= *unaffected

Weaknesses

References