CVE-2026-98532

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

ipv6: do not let ipv6 find hdr() return an offset past the packet end

ipv6 find hdr() walks the extension header chain, skipping each header by the length that header itself declares. ipv6 optlen() returns up to 2048, and the skip is never checked against skb->len, so the offset stored in *offset can point past the end of the packet.

openvswitch installs that offset as the transport header, and update ipv6 checksum() then reads and writes the transport checksum field out of bounds:

BUG: KASAN: slab-use-after-free in inet proto csum replace16+0x445/0x470 Read of size 2 at addr ffff88810b754b06 by task ovs ipv6 oob/629 CPU: 4 UID: 1000 PID: 629 Comm: ovs ipv6 oob Tainted: G N 7.3.0-rc3+ #348 Call Trace: inet proto csum replace16+0x445/0x470 set ipv6 addr+0x3dd/0x460 do execute actions+0x6a3d/0x7c40 ovs execute actions+0xfd/0x480 ovs packet cmd execute+0xc38/0xf20 genl rcv msg+0x59e/0x870 netlink rcv skb+0x18b/0x450 genl rcv+0x2d/0x40 netlink unicast+0x6bc/0xa20

The buggy address belongs to the object at ffff88810b754980 which belongs to the cache skbuff small head of size 704 The buggy address is located 390 bytes inside of freed 704-byte region [ffff88810b754980, ffff88810b754c40)

Other callers use that offset too, so bound it here rather than in one caller.

Reject a header whose declared length does not fit in the packet. ipv6 find hdr() already fails with -EBADMSG on a malformed chain, so this adds no new failure mode.