{"id":"CVE-2026-72254","state":"PUBLISHED","title":"netfilter: nft_fib: reject fib expression on the netdev egress hook","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nft_fib: reject fib expression on the netdev egress hook\n\nA fib expression in a netdev egress base chain dereferences nft_in(pkt),\nNULL on the transmit path, causing a NULL pointer dereference at eval.\nnft_fib_validate() masks the hook with NF_INET_* values, but netdev hook\nnumbers are a separate enum that aliases them (NF_NETDEV_EGRESS ==\nNF_INET_LOCAL_IN), so an egress chain passes validation and then faults.\n\nAdd nft_fib_netdev_validate() that limits each result/flag to the netdev\nhook where the device it reads exists: the input-device cases (OIF,\nOIFNAME, ADDRTYPE with F_IIF) to ingress, the output-device case (ADDRTYPE\nwith F_OIF) to egress, ADDRTYPE with no device flag to both. Also restrict\nnft_fib_validate() to NFPROTO_IPV4/IPV6/INET so its NF_INET_* masks are\nnot applied to another family's hooks.","publishedAt":"2026-08-15T05:54:42.239Z","updatedAt":"2026-10-30T12:28:58.734Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"1258a6da042c0c283dcf5c581acb318db29c760a","versionType":"git"},{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"4fee43759b489559a491f7c95f9bfa7a1d0c7a10","versionType":"git"},{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"568931f26af4727a51e8521f72efbc78d3b82410","versionType":"git"},{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"d01c913febead04a01a5f3a6374d1f45504dc523","versionType":"git"},{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"f68305267ebda7e839b5e8f77e8d77535a3d5a0f","versionType":"git"},{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"d07955dd34ecae17d35d8c7d0a273a3fba653a8c","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nft_fib.c","net/netfilter/nft_fib_netdev.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.16","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.148","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.101","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.42","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nft_fib.c","net/netfilter/nft_fib_netdev.c"]}],"references":["https://git.kernel.org/stable/c/1258a6da042c0c283dcf5c581acb318db29c760a","https://git.kernel.org/stable/c/4fee43759b489559a491f7c95f9bfa7a1d0c7a10","https://git.kernel.org/stable/c/568931f26af4727a51e8521f72efbc78d3b82410","https://git.kernel.org/stable/c/d01c913febead04a01a5f3a6374d1f45504dc523","https://git.kernel.org/stable/c/f68305267ebda7e839b5e8f77e8d77535a3d5a0f","https://git.kernel.org/stable/c/d07955dd34ecae17d35d8c7d0a273a3fba653a8c"],"weaknesses":[],"ingestedAt":"2026-10-30T12:48:04.825Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/72xxx/CVE-2026-72254.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-72254","state":"PUBLISHED","datePublished":"2026-08-15T05:54:42.239Z","dateUpdated":"2026-10-30T12:28:58.734Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-09T03:40:39.915Z"},"containers":{"cna":{"title":"netfilter: nft_fib: reject fib expression on the netdev egress hook","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nft_fib: reject fib expression on the netdev egress hook\n\nA fib expression in a netdev egress base chain dereferences nft_in(pkt),\nNULL on the transmit path, causing a NULL pointer dereference at eval.\nnft_fib_validate() masks the hook with NF_INET_* values, but netdev hook\nnumbers are a separate enum that aliases them (NF_NETDEV_EGRESS ==\nNF_INET_LOCAL_IN), so an egress chain passes validation and then faults.\n\nAdd nft_fib_netdev_validate() that limits each result/flag to the netdev\nhook where the device it reads exists: the input-device cases (OIF,\nOIFNAME, ADDRTYPE with F_IIF) to ingress, the output-device case (ADDRTYPE\nwith F_OIF) to egress, ADDRTYPE with no device flag to both. Also restrict\nnft_fib_validate() to NFPROTO_IPV4/IPV6/INET so its NF_INET_* masks are\nnot applied to another family's hooks."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"1258a6da042c0c283dcf5c581acb318db29c760a","versionType":"git"},{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"4fee43759b489559a491f7c95f9bfa7a1d0c7a10","versionType":"git"},{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"568931f26af4727a51e8521f72efbc78d3b82410","versionType":"git"},{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"d01c913febead04a01a5f3a6374d1f45504dc523","versionType":"git"},{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"f68305267ebda7e839b5e8f77e8d77535a3d5a0f","versionType":"git"},{"version":"42df6e1d221dddc0f2acf2be37e68d553ad65f96","status":"affected","lessThan":"d07955dd34ecae17d35d8c7d0a273a3fba653a8c","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nft_fib.c","net/netfilter/nft_fib_netdev.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.16","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.16","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.148","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.101","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.42","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.5","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nft_fib.c","net/netfilter/nft_fib_netdev.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/1258a6da042c0c283dcf5c581acb318db29c760a"},{"url":"https://git.kernel.org/stable/c/4fee43759b489559a491f7c95f9bfa7a1d0c7a10"},{"url":"https://git.kernel.org/stable/c/568931f26af4727a51e8521f72efbc78d3b82410"},{"url":"https://git.kernel.org/stable/c/d01c913febead04a01a5f3a6374d1f45504dc523"},{"url":"https://git.kernel.org/stable/c/f68305267ebda7e839b5e8f77e8d77535a3d5a0f"},{"url":"https://git.kernel.org/stable/c/d07955dd34ecae17d35d8c7d0a273a3fba653a8c"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - Once a netdev egress fib rule is installed, evaluation runs on the packet transmit datapath (nf_hook_egress in __dev_queue_xmit); a remote peer can trigger it by causing the host to send matching IPv4/IPv6 traffic through the hooked interface, matching prior netfilter CNA treatment of pre-deployed nftables rules (e.g. CVE-2026-52998).\nAC:L - No race or uncontrollable victim state is required; with an affected egress fib rule present, the attacker reliably triggers the NULL dereference on the next matching outbound packet by controlling protocol headers and normal connection traffic.\nPR:N - Runtime exploitation needs only network traffic through the netdev egress hook; although installing the fib rule requires CAP_NET_ADMIN, validation incorrectly accepts it as legal, so orchestration or administrators can deploy it and remote attackers need no target credentials or local privileges.\nUI:N - No victim interaction is required beyond ordinary network traffic processing; the kernel automatically evaluates the fib expression on egress without mounts, file opens, or user prompts.\nS:U - Impact is a kernel NULL-pointer fault and host-wide denial of service within the same kernel/network-filtering security authority; it does not constitute VM escape, IOMMU bypass, or another cross-authority boundary change.\nC:N - The failure mode is a NULL pointer dereference of nft_in(pkt) on egress (in is NULL in nf_hook_state_init); there is no use-after-free, out-of-bounds read, or other attacker-controlled memory disclosure primitive.\nI:N - The bug does not corrupt writable memory or provide control-flow hijack; it only dereferences a NULL input device pointer during fib lookup/skipping and cannot modify kernel or user data beyond the immediate fault.\nA:H - The NULL dereference in nft_fib_netdev_eval/nft_fib4_eval/nft_fib6_eval on netdev egress causes a kernel oops/panic-class fault during packet transmission, denying system availability until reboot."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:28:58.734Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.6.148"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.12.101"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"6.18.42"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"7.1.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.16","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-72254","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T18:45:20.670806Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-16T18:55:13.693Z"}}]}}}