{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74478","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-08-15T05:44:03.903Z","datePublished":"2026-08-15T12:27:12.549Z","dateUpdated":"2026-08-19T16:37:30.555Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-08-19T16:37:30.555Z"},"descriptions":[{"lang":"en","value":"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."}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","baseScore":9.8,"baseSeverity":"CRITICAL"},"scenarios":[{"lang":"en","value":"AV:N - The bug is reached from remotely sent GRE or L2TPv3 packets processed by vector_mmsg_rx() via recvmmsg on the tunnel socket; the fix commit states any peer on those transports can trigger it without authentication.\nAC:L - An attacker reliably triggers verify_header() failure with a wrong GRE key or L2TPv3 session/cookie, and sending two or more malformed packets in one recvmmsg batch causes immediate double-free of the same skb without races or special memory layout.\nPR:N - No privileges on the UML instance are required; exploitation needs only the ability to send network packets on the configured GRE/L2TPv3 transport, and overlay keys/cookies are not authenticated security controls.\nUI:N - Exploitation is driven entirely by remote packets delivered to the vector netdev RX path and requires no victim user or administrator action beyond the interface already being up.\nS:U - The use-after-free corrupts sk_buff memory inside the UML kernel network driver and does not by itself cross a VM, IOMMU, or host-kernel security boundary.\nC:H - The refcount underflow/use-after-free leaves a dangling sk_buff pointer that can be reallocated and read through standard heap grooming, giving an arbitrary kernel memory disclosure primitive.\nI:H - Reclaiming the freed sk_buff enables attacker-controlled contents in kernel heap objects and can be leveraged for arbitrary write or control-flow hijack in the UML kernel context.\nA:H - The double-free in the RX path can immediately oops or panic the UML kernel, and an unauthenticated remote peer can retrigger the condition by sending additional malformed tunnel packets."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/um/drivers/vector_kern.c"],"versions":[{"version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","lessThan":"967c779c9853d2a1cc9cd8e61d300250c348f3d9","status":"affected","versionType":"git"},{"version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","lessThan":"a7bc015bb798c525e7a82dd14225c6aeb994274b","status":"affected","versionType":"git"},{"version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","lessThan":"7dc9781e320d664c9bdd50003c9acfddf363d1e1","status":"affected","versionType":"git"},{"version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","lessThan":"4b9601595e8b6b5d18878cac0aeabc687d241111","status":"affected","versionType":"git"},{"version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","lessThan":"67d58ab4f2ccf7145f3da07e025735a09c79de1b","status":"affected","versionType":"git"},{"version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","lessThan":"180ff4c81faf01ec4e06082c9daa7c40518ead89","status":"affected","versionType":"git"},{"version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","lessThan":"804b681002ead233abf49a3efd681f5468a835f9","status":"affected","versionType":"git"},{"version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","lessThan":"af421e9aed3920c7ac88c24daa48606c7112feca","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["arch/um/drivers/vector_kern.c"],"versions":[{"version":"4.17","status":"affected"},{"version":"0","lessThan":"4.17","status":"unaffected","versionType":"semver"},{"version":"5.10.265","lessThanOrEqual":"5.10.*","status":"unaffected","versionType":"semver"},{"version":"5.15.216","lessThanOrEqual":"5.15.*","status":"unaffected","versionType":"semver"},{"version":"6.1.183","lessThanOrEqual":"6.1.*","status":"unaffected","versionType":"semver"},{"version":"6.6.151","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.103","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.44","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.1.8","lessThanOrEqual":"7.1.*","status":"unaffected","versionType":"semver"},{"version":"7.2","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"5.10.265"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"5.15.216"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.1.183"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.6.151"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.12.103"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"6.18.44"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"7.1.8"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.17","versionEndExcluding":"7.2"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/967c779c9853d2a1cc9cd8e61d300250c348f3d9"},{"url":"https://git.kernel.org/stable/c/a7bc015bb798c525e7a82dd14225c6aeb994274b"},{"url":"https://git.kernel.org/stable/c/7dc9781e320d664c9bdd50003c9acfddf363d1e1"},{"url":"https://git.kernel.org/stable/c/4b9601595e8b6b5d18878cac0aeabc687d241111"},{"url":"https://git.kernel.org/stable/c/67d58ab4f2ccf7145f3da07e025735a09c79de1b"},{"url":"https://git.kernel.org/stable/c/180ff4c81faf01ec4e06082c9daa7c40518ead89"},{"url":"https://git.kernel.org/stable/c/804b681002ead233abf49a3efd681f5468a835f9"},{"url":"https://git.kernel.org/stable/c/af421e9aed3920c7ac88c24daa48606c7112feca"}],"title":"um: vector: fix use-after-free in vector_mmsg_rx()","x_generator":{"engine":"bippy-1.2.0"}}}}