{"api_version":"1","generated_at":"2026-08-17T10:19:03+00:00","cve":"CVE-2026-74478","urls":{"html":"https://cve.report/CVE-2026-74478","api":"https://cve.report/api/cve/CVE-2026-74478.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-74478","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-74478"},"summary":{"title":"um: vector: fix use-after-free in vector_mmsg_rx()","description":"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.","state":"PUBLISHED","assigner":"Linux","published_at":"2026-08-15 13:17:52","updated_at":"2026-08-17 06:19:43"},"problem_types":[],"metrics":[{"version":"3.1","source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","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","data":{"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","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"}},{"version":"3.1","source":"CNA","type":"DECLARED","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","data":{"baseScore":9.8,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}}],"references":[{"url":"https://git.kernel.org/stable/c/af421e9aed3920c7ac88c24daa48606c7112feca","name":"https://git.kernel.org/stable/c/af421e9aed3920c7ac88c24daa48606c7112feca","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/804b681002ead233abf49a3efd681f5468a835f9","name":"https://git.kernel.org/stable/c/804b681002ead233abf49a3efd681f5468a835f9","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/180ff4c81faf01ec4e06082c9daa7c40518ead89","name":"https://git.kernel.org/stable/c/180ff4c81faf01ec4e06082c9daa7c40518ead89","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/67d58ab4f2ccf7145f3da07e025735a09c79de1b","name":"https://git.kernel.org/stable/c/67d58ab4f2ccf7145f3da07e025735a09c79de1b","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://git.kernel.org/stable/c/4b9601595e8b6b5d18878cac0aeabc687d241111","name":"https://git.kernel.org/stable/c/4b9601595e8b6b5d18878cac0aeabc687d241111","refsource":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-74478","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74478","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb 4b9601595e8b6b5d18878cac0aeabc687d241111 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb 67d58ab4f2ccf7145f3da07e025735a09c79de1b git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb 180ff4c81faf01ec4e06082c9daa7c40518ead89 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb 804b681002ead233abf49a3efd681f5468a835f9 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 49da7e64f33e80edffb1a9eeb230fa4c3f42dffb af421e9aed3920c7ac88c24daa48606c7112feca git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 4.17","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 4.17 semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.6.151 6.6.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.12.103 6.12.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 6.18.44 6.18.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.1.8 7.1.* semver","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"unaffected 7.2 * original_commit_for_fix","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":{"cve_year":"2026","cve_id":"74478","cve":"CVE-2026-74478","epss":"0.002010000","percentile":"0.103740000","score_date":"2026-08-16","updated_at":"2026-08-17 00:01:04"},"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"defaultStatus":"unaffected","product":"Linux","programFiles":["arch/um/drivers/vector_kern.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"lessThan":"4b9601595e8b6b5d18878cac0aeabc687d241111","status":"affected","version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","versionType":"git"},{"lessThan":"67d58ab4f2ccf7145f3da07e025735a09c79de1b","status":"affected","version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","versionType":"git"},{"lessThan":"180ff4c81faf01ec4e06082c9daa7c40518ead89","status":"affected","version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","versionType":"git"},{"lessThan":"804b681002ead233abf49a3efd681f5468a835f9","status":"affected","version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","versionType":"git"},{"lessThan":"af421e9aed3920c7ac88c24daa48606c7112feca","status":"affected","version":"49da7e64f33e80edffb1a9eeb230fa4c3f42dffb","versionType":"git"}]},{"defaultStatus":"affected","product":"Linux","programFiles":["arch/um/drivers/vector_kern.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","vendor":"Linux","versions":[{"status":"affected","version":"4.17"},{"lessThan":"4.17","status":"unaffected","version":"0","versionType":"semver"},{"lessThanOrEqual":"6.6.*","status":"unaffected","version":"6.6.151","versionType":"semver"},{"lessThanOrEqual":"6.12.*","status":"unaffected","version":"6.12.103","versionType":"semver"},{"lessThanOrEqual":"6.18.*","status":"unaffected","version":"6.18.44","versionType":"semver"},{"lessThanOrEqual":"7.1.*","status":"unaffected","version":"7.1.8","versionType":"semver"},{"lessThanOrEqual":"*","status":"unaffected","version":"7.2","versionType":"original_commit_for_fix"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.6.151","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.12.103","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"6.18.44","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.1.8","versionStartIncluding":"4.17","vulnerable":true},{"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionEndExcluding":"7.2","versionStartIncluding":"4.17","vulnerable":true}],"negate":false,"operator":"OR"}]}],"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":{"baseScore":9.8,"baseSeverity":"CRITICAL","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"},"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."}]}],"providerMetadata":{"dateUpdated":"2026-08-17T05:47:38.560Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"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"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2026-74478","datePublished":"2026-08-15T12:27:12.549Z","dateReserved":"2026-08-15T05:44:03.903Z","dateUpdated":"2026-08-17T05:47:38.560Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-15 13:17:52","lastModifiedDate":"2026-08-17 06:19:43","problem_types":[],"metrics":{"cvssMetricV31":[{"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","type":"Secondary","cvssData":{"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","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":5.9}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"74478","Ordinal":"1","Title":"um: vector: fix use-after-free in vector_mmsg_rx()","CVE":"CVE-2026-74478","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"74478","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"um: vector: fix use-after-free in vector_mmsg_rx()"}]}}}