{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-93250","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-17T16:02:15.096Z","datePublished":"2026-09-24T15:51:15.108Z","dateUpdated":"2026-09-25T05:09:51.783Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-25T05:09:51.783Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: mdb: Fix use-after-free in vxlan_mdb_flush()\n\nvxlan_mdb_flush() iterates over the MDB entries using\nhlist_for_each_entry_safe(), which only tolerates the removal of the\ncurrent entry. Contrary to the comment above the loop, the removal of an\nentry can trigger the removal of another entry.\n\nFlushing the remotes of a (*, G) entry also removes the (S, G) entries\nthat were created for its source list, once they are left without\nremotes:\n\nvxlan_mdb_remotes_flush()\n-> vxlan_mdb_remote_del()\n   -> vxlan_mdb_remote_srcs_del()\n      -> vxlan_mdb_remote_src_del()\n         -> vxlan_mdb_remote_src_fwd_del()\n            -> __vxlan_mdb_del()\n               -> vxlan_mdb_entry_put()\n\nSuch an entry can be located after the (*, G) entry in the list, as\nvxlan_mdb_entry_get() returns an existing entry without moving it to the\nhead of the list. This order is obtained by adding the (S, G) entry\nbefore the (*, G) entry, the latter with NLM_F_REPLACE, as the addition\nof the source otherwise fails with -EEXIST. The (S, G) entry is then the\nentry saved by hlist_for_each_entry_safe() and it is freed while the\n(*, G) entry is processed. The next iteration calls hlist_del() on it\nagain, writing LIST_POISON1 to LIST_POISON2 [1].\n\nBesides device deletion, the flush is also reachable from RTM_DELMDB\nwith NLM_F_BULK.\n\nFix by re-reading the next entry after the remotes were flushed. The\ncurrent entry cannot be removed by this flush, as source lists can only\nbe configured on (*, G) entries and the removed entries are (S, G)\nentries. It is therefore still linked and its next pointer reflects the\nremovals.\n\n[1]\nBUG: KASAN: wild-memory-access in vxlan_mdb_entry_put.part.0+0x328/0x588\nWrite of size 8 at addr dead000000000122 by task ip/327\n\nCPU: 3 UID: 1000 PID: 327 Comm: ip Not tainted 7.2.0-rc7 #2 PREEMPT\nCall trace:\n vxlan_mdb_entry_put.part.0+0x328/0x588\n vxlan_mdb_flush+0x1d8/0x25c\n vxlan_mdb_fini+0x8c/0x100\n vxlan_uninit+0x1c/0x7c\n unregister_netdevice_many_notify+0x954/0xd4c\n rtnl_dellink+0x210/0x530\n rtnetlink_rcv_msg+0x434/0x4d0\n netlink_rcv_skb+0xc4/0x204\n rtnetlink_rcv+0x18/0x24\n netlink_unicast+0x4b8/0x548\n netlink_sendmsg+0x29c/0x560\n ____sys_sendmsg+0x390/0x3ec\n ___sys_sendmsg+0x114/0x188\n __sys_sendmsg+0xf0/0x178\n __arm64_sys_sendmsg+0x48/0x60\n invoke_syscall.constprop.0+0x58/0x180\n el0_svc_common.constprop.0+0x74/0x140\n do_el0_svc+0x30/0x40\n el0_svc+0x38/0x98\n el0t_64_sync_handler+0xa0/0xe4\n el0t_64_sync+0x198/0x19c"}],"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 UAF is in vxlan_mdb_flush(), reached from local NETLINK_ROUTE sendmsg via rtnl_dellink→vxlan_uninit→vxlan_mdb_fini, or rtnl_mdb_del(RTM_DELMDB|NLM_F_BULK)→vxlan_mdb_del_bulk. Received VXLAN UDP uses vxlan_mdb_entry_skb_get/vxlan_mdb_xmit and never calls flush, so the trigger is the netlink control message, not a peer packet.\nAC:L - The attacker builds the bad mdb_list order themselves: RTM_NEWMDB adds an (S,G) entry, then RTM_NEWMDB with NLM_F_REPLACE adds a (*,G) whose source list reuses that (S,G) via vxlan_mdb_entry_get() without moving it to the list head, then RTM_DELLINK or RTM_DELMDB|NLM_F_BULK runs vxlan_mdb_flush(). No race or victim-side state is required.\nPR:L - rtnetlink_rcv_msg requires netlink_net_capable(CAP_NET_ADMIN) for RTM_NEWLINK/RTM_NEWMDB/RTM_DELMDB/RTM_DELLINK, i.e. CAP_NET_ADMIN in the socket netns user_ns, obtained via unshare -Urn. vxlan_link_ops has no extra capability gate, and the KASAN trace ran as UID 1000 (ip).\nUI:N - The attacker issues their own rtnetlink messages to create the vxlan, add the (S,G) then (*,G) MDB entries, and trigger vxlan_mdb_flush() via RTM_DELLINK or RTM_DELMDB NLM_F_BULK; no victim mount, click, or other action is required.\nS:U - The freed object is a kmalloc'd vxlan_mdb_entry processed under RTNL in the same kernel that handled the netlink command; impact is host-kernel memory corruption, not a VM escape, IOMMU bypass, or other changed-scope boundary.\nC:H - vxlan_mdb_entry_put() kfree_rcu's the (S,G) vxlan_mdb_entry while hlist_for_each_entry_safe() still holds it in tmp; the next vxlan_mdb_flush() iteration then reads that slab object (key.vni and remotes). After RCU reclaim the same kmalloc slot can be sprayed for an arbitrary kernel read.\nI:H - The stale tmp then re-enters vxlan_mdb_entry_put(), which hlist_del()s the already-unlinked mdb_node (WRITE_ONCE through LIST_POISON2 or a sprayed pprev) and would kfree_rcu the same vxlan_mdb_entry twice, giving a slab double-free write primitive.\nA:H - KASAN reports a wild-memory-access 8-byte write to LIST_POISON2 (dead000000000122) in vxlan_mdb_entry_put() from vxlan_mdb_flush() during rtnl_dellink of the vxlan, which oopses the kernel."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/vxlan/vxlan_mdb.c"],"versions":[{"version":"a3a48de5eade770e911d35291217bdd69ce04ef1","lessThan":"f8a9b988e7a7bc674e74e8c901794d792c35689e","status":"affected","versionType":"git"},{"version":"a3a48de5eade770e911d35291217bdd69ce04ef1","lessThan":"c7dc26d06f90ca11bbd6114f6a62a67d038816c7","status":"affected","versionType":"git"},{"version":"a3a48de5eade770e911d35291217bdd69ce04ef1","lessThan":"3e6b705bc162fc7257645725a7d2cf6c71250318","status":"affected","versionType":"git"},{"version":"a3a48de5eade770e911d35291217bdd69ce04ef1","lessThan":"f26400b325bdc2868e40612c4804c82cf8ba6275","status":"affected","versionType":"git"},{"version":"a3a48de5eade770e911d35291217bdd69ce04ef1","lessThan":"bc2dc66a6693a78f8c1e6ca2dbebd50f16e2c366","status":"affected","versionType":"git"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/net/vxlan/vxlan_mdb.c"],"versions":[{"version":"6.4","status":"affected"},{"version":"0","lessThan":"6.4","status":"unaffected","versionType":"semver"},{"version":"6.6.157","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.110","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.52","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.6","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3-rc1","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":"6.4","versionEndExcluding":"6.6.157"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.12.110"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.18.52"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.2.6"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.3-rc1"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/f8a9b988e7a7bc674e74e8c901794d792c35689e"},{"url":"https://git.kernel.org/stable/c/c7dc26d06f90ca11bbd6114f6a62a67d038816c7"},{"url":"https://git.kernel.org/stable/c/3e6b705bc162fc7257645725a7d2cf6c71250318"},{"url":"https://git.kernel.org/stable/c/f26400b325bdc2868e40612c4804c82cf8ba6275"},{"url":"https://git.kernel.org/stable/c/bc2dc66a6693a78f8c1e6ca2dbebd50f16e2c366"}],"title":"vxlan: mdb: Fix use-after-free in vxlan_mdb_flush()","x_generator":{"engine":"bippy-1.2.0"}}}}