{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-74561", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.916Z", "datePublished": "2026-08-15T12:28:04.525Z", "dateUpdated": "2026-10-15T10:09:15.073Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-15T10:09:15.073Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnexthop: avoid unlocked f6i_list walk in nh_rt_cache_flush\n\nnh_rt_cache_flush() walks nh->f6i_list during an RTNL-serialized nexthop\nreplace without holding nh->lock, racing the unlocked IPv6 route\nadd/delete that mutate the list under nh->lock and free fib6_info\nentries (nh_rt_cache_flush() is inlined into rtm_new_nexthop()):\n\n BUG: KASAN: slab-use-after-free in nh_rt_cache_flush (net/ipv4/nexthop.c:2243)\n Read of size 8 at addr ffff888012953e18 by task exploit/146\n nh_rt_cache_flush (net/ipv4/nexthop.c:2243)\n replace_nexthop (net/ipv4/nexthop.c:2610)\n rtm_new_nexthop (net/ipv4/nexthop.c:3323)\n rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)\n\nUnlike the other f6i_list walks, this one bumps each route's sernum via\nfib6_update_sernum_upto_root(), which needs tb6_lock; taking nh->lock\naround it would invert the established tb6_lock -> nh->lock order and\ndeadlock. As the only purpose is to invalidate cached dsts, bump the\nIPv6 sernum for the whole netns with rt_genid_bump_ipv6() instead,\nmirroring the rt_cache_flush() already done for IPv4 just above." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - The slab use-after-free is reached only via local RTNETLINK on AF_NETLINK sockets: RTM_NEWNEXTHOP with NLM_F_REPLACE drives replace_nexthop()->nh_rt_cache_flush(), racing concurrent RTM_NEWROUTE/RTM_DELROUTE IPv6 route changes; it is not triggered by remote packet processing.\nAC:L - The race is attacker-controlled: one thread replaces a nexthop under rtnl_net_lock while another concurrently adds/deletes IPv6 routes via unlocked inet6_rtm_newroute/inet6_rtm_delroute handlers; Microsoft reproduced reliable KASAN slab-use-after-free with this pattern.\nPR:L - rtnetlink_rcv_msg() requires CAP_NET_ADMIN via netlink_net_capable() for all non-GET handlers; unprivileged local users obtain this inside a user/network namespace (unshare -Urn), not only init-namespace root.\nUI:N - No victim interaction is required; exploitation is fully attacker-driven through coordinated local netlink nexthop replace and IPv6 route add/delete commands from attacker-controlled processes.\nS:C - A successful UAF from CAP_NET_ADMIN inside an unprivileged user/network namespace corrupts host kernel slab memory and can escape the namespace/container sandbox to compromise the host system, crossing the container-to-host security boundary.\nC:H - The unlocked nh->f6i_list walk dereferences freed fib6_info objects (KASAN read of size 8 at nh_rt_cache_flush), enabling arbitrary kernel memory disclosure via slab heap reuse of attacker-groomed objects.\nI:H - Beyond the UAF read, fib6_update_sernum_upto_root() writes fn_sernum through stale fib6_info/fib6_table pointers; slab UAF on fib6_info provides memory corruption primitives for arbitrary kernel writes and local privilege escalation.\nA:H - The confirmed KASAN slab-use-after-free in nh_rt_cache_flush during nexthop replace causes kernel oops/panic; UAF list walks are inherently crash-prone and can be triggered repeatedly for denial of service." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv4/nexthop.c" ], "versions": [ { "version": "081efd18326e353c6fbfdeff903a83edde953f72", "lessThan": "f97fae992155b11da516a509c855ff9d0868b107", "status": "affected", "versionType": "git" }, { "version": "081efd18326e353c6fbfdeff903a83edde953f72", "lessThan": "44f53e4331a30fabc38a411fae7524341b618db3", "status": "affected", "versionType": "git" }, { "version": "081efd18326e353c6fbfdeff903a83edde953f72", "lessThan": "4787a6d2629b4e8c0b6bacab1f75c1660eca44d9", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv4/nexthop.c" ], "versions": [ { "version": "6.16", "status": "affected" }, { "version": "0", "lessThan": "6.16", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.57", "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": "6.16", "versionEndExcluding": "6.18.57" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "7.1.8" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/f97fae992155b11da516a509c855ff9d0868b107" }, { "url": "https://git.kernel.org/stable/c/44f53e4331a30fabc38a411fae7524341b618db3" }, { "url": "https://git.kernel.org/stable/c/4787a6d2629b4e8c0b6bacab1f75c1660eca44d9" } ], "title": "nexthop: avoid unlocked f6i_list walk in nh_rt_cache_flush", "x_generator": { "engine": "bippy-1.2.0" } } } }