CVE-2026-74478

Technical Description

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

um: vector: fix use-after-free in vector_mmsg_rx()

When vector_mmsg_rx() discards a packet whose overlay header fails

verify_header(), it frees the skb and continues the loop:

if (header_check < 0) {

dev_kfree_skb_irq(skb);

vp->estats.rx_encaps_errors++;

continue;

}

The normal and short-packet paths fall through to the bottom of the

loop body, which clears the consumed slot and advances the cursors:

(*skbuff_vector) = NULL;

mmsg_vector++;

skbuff_vector++;

The verify_header() < 0 path skips that via continue, so the freed skb

is left in skbuff_vector[] and the cursors do not advance. The next

iteration reads the same slot, gets the freed skb, and frees it again,

producing a refcount underflow / use-after-free in the RX path.

Discard the slot the same way the other paths do before continuing.

Only transports whose verify_header() can return negative are affected:

GRE and L2TPv3 do so on a cookie/sessio

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References