{"id":"CVE-2026-43374","state":"PUBLISHED","title":"net: nexthop: fix percpu use-after-free in remove_nh_grp_entry","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: nexthop: fix percpu use-after-free in remove_nh_grp_entry\n\nWhen removing a nexthop from a group, remove_nh_grp_entry() publishes\nthe new group via rcu_assign_pointer() then immediately frees the\nremoved entry's percpu stats with free_percpu(). However, the\nsynchronize_net() grace period in the caller remove_nexthop_from_groups()\nruns after the free. RCU readers that entered before the publish still\nsee the old group and can dereference the freed stats via\nnh_grp_entry_stats_inc() -> get_cpu_ptr(nhge->stats), causing a\nuse-after-free on percpu memory.\n\nFix by deferring the free_percpu() until after synchronize_net() in the\ncaller. Removed entries are chained via nh_list onto a local deferred\nfree list. After the grace period completes and all RCU readers have\nfinished, the percpu stats are safely freed.","publishedAt":"2026-05-08T14:21:24.537Z","updatedAt":"2026-10-19T19:16:28.049Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f4676ea74b8549cd88dbfe2a592ce4530039e61f","status":"affected","lessThan":"abf4feaee6405f1441929c6ebe7a250f2cd170a7","versionType":"git"},{"version":"f4676ea74b8549cd88dbfe2a592ce4530039e61f","status":"affected","lessThan":"ab5ebab9664214ba41a7633cb4e72f128204f924","versionType":"git"},{"version":"f4676ea74b8549cd88dbfe2a592ce4530039e61f","status":"affected","lessThan":"9e08ad731862b22a87cc55f752e16d66cdc9e231","versionType":"git"},{"version":"f4676ea74b8549cd88dbfe2a592ce4530039e61f","status":"affected","lessThan":"b2662e7593e94ae09b1cf7ee5f09160a3612bcb2","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/nexthop.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.9","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.19","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.9","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/nexthop.c"]}],"references":["https://git.kernel.org/stable/c/abf4feaee6405f1441929c6ebe7a250f2cd170a7","https://git.kernel.org/stable/c/ab5ebab9664214ba41a7633cb4e72f128204f924","https://git.kernel.org/stable/c/9e08ad731862b22a87cc55f752e16d66cdc9e231","https://git.kernel.org/stable/c/b2662e7593e94ae09b1cf7ee5f09160a3612bcb2"],"weaknesses":["CWE-416"],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/43xxx/CVE-2026-43374.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-43374","state":"PUBLISHED","datePublished":"2026-05-08T14:21:24.537Z","dateUpdated":"2026-10-19T19:16:28.049Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-05-01T14:12:56.006Z"},"containers":{"cna":{"title":"net: nexthop: fix percpu use-after-free in remove_nh_grp_entry","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: nexthop: fix percpu use-after-free in remove_nh_grp_entry\n\nWhen removing a nexthop from a group, remove_nh_grp_entry() publishes\nthe new group via rcu_assign_pointer() then immediately frees the\nremoved entry's percpu stats with free_percpu(). However, the\nsynchronize_net() grace period in the caller remove_nexthop_from_groups()\nruns after the free. RCU readers that entered before the publish still\nsee the old group and can dereference the freed stats via\nnh_grp_entry_stats_inc() -> get_cpu_ptr(nhge->stats), causing a\nuse-after-free on percpu memory.\n\nFix by deferring the free_percpu() until after synchronize_net() in the\ncaller. Removed entries are chained via nh_list onto a local deferred\nfree list. After the grace period completes and all RCU readers have\nfinished, the percpu stats are safely freed."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f4676ea74b8549cd88dbfe2a592ce4530039e61f","status":"affected","lessThan":"abf4feaee6405f1441929c6ebe7a250f2cd170a7","versionType":"git"},{"version":"f4676ea74b8549cd88dbfe2a592ce4530039e61f","status":"affected","lessThan":"ab5ebab9664214ba41a7633cb4e72f128204f924","versionType":"git"},{"version":"f4676ea74b8549cd88dbfe2a592ce4530039e61f","status":"affected","lessThan":"9e08ad731862b22a87cc55f752e16d66cdc9e231","versionType":"git"},{"version":"f4676ea74b8549cd88dbfe2a592ce4530039e61f","status":"affected","lessThan":"b2662e7593e94ae09b1cf7ee5f09160a3612bcb2","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/nexthop.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.9","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.9","versionType":"semver"},{"version":"6.12.78","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.19","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"6.19.9","status":"unaffected","lessThanOrEqual":"6.19.*","versionType":"semver"},{"version":"7.0","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/ipv4/nexthop.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/abf4feaee6405f1441929c6ebe7a250f2cd170a7"},{"url":"https://git.kernel.org/stable/c/ab5ebab9664214ba41a7633cb4e72f128204f924"},{"url":"https://git.kernel.org/stable/c/9e08ad731862b22a87cc55f752e16d66cdc9e231"},{"url":"https://git.kernel.org/stable/c/b2662e7593e94ae09b1cf7ee5f09160a3612bcb2"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The freeing side is reached through `RTM_DELNEXTHOP` over rtnetlink, which is a local netlink configuration interface. Remote packets can hit the RCU read side, but an attacker must locally trigger nexthop deletion to create the UAF.\nAC:L - A local attacker can create nexthop groups, attach routes, generate concurrent route lookups, and delete a member nexthop, controlling both sides of the race. The bug is a straightforward RCU grace-period violation rather than a condition dependent on external state.\nPR:L - The rtnetlink non-GET path requires `CAP_NET_ADMIN` in the socket's network namespace. Because this is reachable with namespaced `CAP_NET_ADMIN` via user/network namespaces on affected systems, this is Low rather than High.\nUI:N - No victim interaction is required once the attacker has local access and the needed namespace capability. The attacker can perform the netlink operations and traffic generation directly.\nS:U - The vulnerability corrupts kernel memory within the same kernel security authority. It is a kernel privilege-impact bug, not a VM escape or cross-scope boundary bypass.\nC:H - This is a use-after-free of per-CPU nexthop group statistics reachable from RCU route readers. Following kernel CVSS guidance, UAF memory corruption is treated as enabling high confidentiality impact.\nI:H - The stale reader writes packet counters and sequence state through a freed per-CPU pointer, creating memory corruption that can plausibly be shaped into write/control-flow impact. Per the required guidance, UAF is scored as High integrity impact.\nA:H - The stale dereference of freed per-CPU memory can crash or otherwise destabilize the kernel. Any kernel UAF with crash potential is High availability impact."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:27:34.663Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"6.12.78"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"6.18.19"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"6.19.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.9","versionEndExcluding":"7.0"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-43374","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"total"}],"version":"2.0.3","timestamp":"2026-10-16T15:16:55.959084Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-416","lang":"en","type":"CWE","description":"CWE-416 Use After Free"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T19:16:28.049Z"}}]}}}