{ "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": "2026-10-19T09:08:03.974Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T09:08:03.974Z" }, "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", "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" } ] } ] } ], "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" } } } }