{"id":"CVE-2026-74478","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-74478","summary":"um: vector: fix use-after-free in vector_mmsg_rx()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\num: vector: fix use-after-free in vector_mmsg_rx()\n\nWhen vector_mmsg_rx() discards a packet whose overlay header fails\nverify_header(), it frees the skb and continues the loop:\n\n\tif (header_check < 0) {\n\t\tdev_kfree_skb_irq(skb);\n\t\tvp->estats.rx_encaps_errors++;\n\t\tcontinue;\n\t}\n\nThe normal and short-packet paths fall through to the bottom of the\nloop body, which clears the consumed slot and advances the cursors:\n\n\t(*skbuff_vector) = NULL;\n\tmmsg_vector++;\n\tskbuff_vector++;\n\nThe verify_header() < 0 path skips that via continue, so the freed skb\nis left in skbuff_vector[] and the cursors do not advance. The next\niteration reads the same slot, gets the freed skb, and frees it again,\nproducing a refcount underflow / use-after-free in the RX path.\n\nDiscard the slot the same way the other paths do before continuing.\n\nOnly transports whose verify_header() can return negative are affected:\nGRE and L2TPv3 do so on a cookie/session-id mismatch (raw/tap do not),\nso any peer on such a transport can trigger it without authentication.","published":"2026-08-15T12:27:12.549Z","modified":"2026-08-18T03:56:57.966348453Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Linux","name":"Kernel","fixedVersion":"6.6.151"}],"fix":null,"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/180ff4c81faf01ec4e06082c9daa7c40518ead89"},{"type":"WEB","url":"https://git.kernel.org/stable/c/4b9601595e8b6b5d18878cac0aeabc687d241111"},{"type":"WEB","url":"https://git.kernel.org/stable/c/67d58ab4f2ccf7145f3da07e025735a09c79de1b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/804b681002ead233abf49a3efd681f5468a835f9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/af421e9aed3920c7ac88c24daa48606c7112feca"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74478.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74478"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-18T03:56:57.966348453Z"}}