CVE-2026-74478
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…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.57%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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/session-id mismatch (raw/tap do not), so any peer on such a transport can trigger it without authentication.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.57% probability · 46th percentile
- CISA KEV
- Not listed
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/180ff4c81faf01ec4e06082c9daa7c40518ead89
- https://git.kernel.org/stable/c/4b9601595e8b6b5d18878cac0aeabc687d241111
- https://git.kernel.org/stable/c/67d58ab4f2ccf7145f3da07e025735a09c79de1b
- https://git.kernel.org/stable/c/7dc9781e320d664c9bdd50003c9acfddf363d1e1
- https://git.kernel.org/stable/c/804b681002ead233abf49a3efd681f5468a835f9
- https://git.kernel.org/stable/c/967c779c9853d2a1cc9cd8e61d300250c348f3d9
- https://git.kernel.org/stable/c/a7bc015bb798c525e7a82dd14225c6aeb994274b
- https://git.kernel.org/stable/c/af421e9aed3920c7ac88c24daa48606c7112feca
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.