{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98122","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-25T10:25:14.318Z","datePublished":"2026-09-25T10:36:05.369Z","dateUpdated":"2026-10-03T11:02:33.538Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-10-03T11:02:33.538Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nvxlan: mdb: Fix use-after-free in vxlan_mdb_remote_src_del()\n\nvxlan_mdb_is_valid_source(), which validates MDBE_ATTR_SOURCE and every\nMDBE_ATTR_SRC_LIST member, accepts the all-zeros address.\n\nA source list is only accepted on a (*, G) entry, whose source is the\nall-zeros address, and for each member of the list an (S, G) entry is\nderived from it by substituting the source. Entries are keyed by a plain\nmemcmp() of struct vxlan_mdb_entry_key, so if MDBE_ATTR_SOURCE is present\nand holds the all-zeros address and the source list holds it as well, the\nderived (S, G) key is byte-identical to the (*, G) key and resolves to the\nsame entry. Omitting MDBE_ATTR_SOURCE is not equivalent, as the key is\nthen left with a zero address family.\n\nvxlan_mdb_remote_src_del() removes the forwarding entry of a source before\nfreeing the source entry:\n\n\tvxlan_mdb_remote_src_fwd_del(vxlan, group, remote, &ent->addr);\n\tvxlan_mdb_remote_src_entry_del(ent);\n\nWith the keys aliased, the first call deletes the remote of the entry that\nowns 'ent' instead of a separate (S, G) entry, and frees 'ent'. The second\ncall then runs on the freed entry, and its hlist_del() reads ->pprev and\n->next out of it and writes through them.\n\nAdding the (*, G) entry with NLM_F_REPLACE and no source list marks the\nall-zeros source for deletion and reaches this from the sweep at the end\nof vxlan_mdb_remote_srcs_replace().\n\n  BUG: KASAN: slab-use-after-free in __vxlan_mdb_add+0x1cd/0xd70\n  Read of size 8 at addr ffff888102852500 by task poc/84\n   __vxlan_mdb_add+0x1cd/0xd70\n   vxlan_mdb_add+0xc0/0x140\n   rtnl_mdb_add+0x157/0x2a0\n   rtnetlink_rcv_msg+0x207/0x5a0\n  Allocated by task 84:\n   __kmalloc_cache_noprof+0x153/0x360\n   vxlan_mdb_remote_srcs_add+0x2eb/0x440\n   __vxlan_mdb_add+0x803/0xd70\n  Freed by task 84:\n   kfree+0x14c/0x3b0\n   vxlan_mdb_remote_del+0x129/0x1a0\n   __vxlan_mdb_del+0x4f/0xe0\n   vxlan_mdb_remote_src_fwd_del.isra.0+0x162/0x1b0\n   __vxlan_mdb_add+0x1c5/0xd70\n\nThe MDB operations are netns-scoped, so an unprivileged user can perform\nthem in a new user and network namespace.\n\nReject the all-zeros address in vxlan_mdb_is_valid_source(), which covers\nboth call sites. A (*, G) entry is expressed by omitting the source, so\nnothing legitimate is refused.\n\nDiscovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>"}],"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 malformed input is an RTM_NEWMDB rtnetlink message sent from a local socket (rtnl_mdb_add -> vxlan_mdb_add -> __vxlan_mdb_add -> vxlan_mdb_remote_srcs_replace -> vxlan_mdb_remote_src_del); no packet received from the network reaches the MDB control path.\nAC:L - It is deterministic, with no race: add a (*, G) entry with MDBE_ATTR_SOURCE 0.0.0.0 and 0.0.0.0 in MDBE_ATTR_SRC_LIST, then re-add it with NLM_F_REPLACE and no source list. The attacker creates every piece of the required state.\nPR:L - The only check is netlink_net_capable(CAP_NET_ADMIN) in rtnetlink_rcv_msg, which is namespace-scoped. An unprivileged user can get it with unshare -Urn, create their own vxlan device and send RTM_NEWMDB to it.\nUI:N - The attacker's own netlink messages, on a vxlan device they created in their own namespace, trigger the bug; no other user has to do anything.\nS:U - Corrupting kernel heap memory gives kernel-level impact within the same security authority, which is ordinary local privilege escalation with no VM or hardware boundary crossed.\nC:H - A heap spray can reclaim the freed vxlan_mdb_src_entry before vxlan_mdb_remote_src_entry_del reads it, so the attacker controls the pointers the kernel then uses. This is a slab use-after-free that can be built into a kernel memory disclosure.\nI:H - hlist_del() in vxlan_mdb_remote_src_entry_del reads ->next and ->pprev from the freed entry and writes through them. Once the slot is reclaimed with controlled data, that is an attacker-directed pointer write (an unlink write primitive).\nA:H - Unlinking a freed hlist node corrupts kernel memory; KASAN reports it in __vxlan_mdb_add, and without KASAN the corrupted list pointers can oops or panic the kernel. Any user who can open a user namespace can trigger it repeatedly."}]}],"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","tools/testing/selftests/net/test_vxlan_mdb.sh"],"versions":[{"version":"a3a48de5eade770e911d35291217bdd69ce04ef1","lessThan":"069d5527bb0f229e528fa88c6b72f15060c373f2","status":"affected","versionType":"git"},{"version":"a3a48de5eade770e911d35291217bdd69ce04ef1","lessThan":"e12c903fd13c6261b98ca18d8f70ac26e739e2f8","status":"affected","versionType":"git"},{"version":"a3a48de5eade770e911d35291217bdd69ce04ef1","lessThan":"74e2a56c82209b0335b53e25f19f9b0590e2483d","status":"affected","versionType":"git"},{"version":"a3a48de5eade770e911d35291217bdd69ce04ef1","lessThan":"71203a41d6fa2fa0ea2f3a7541987958bd3694fd","status":"affected","versionType":"git"},{"version":"a3a48de5eade770e911d35291217bdd69ce04ef1","lessThan":"4aa61c88b4e292e10abdfd791334b8272108d68a","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","tools/testing/selftests/net/test_vxlan_mdb.sh"],"versions":[{"version":"6.4","status":"affected"},{"version":"0","lessThan":"6.4","status":"unaffected","versionType":"semver"},{"version":"6.6.158","lessThanOrEqual":"6.6.*","status":"unaffected","versionType":"semver"},{"version":"6.12.111","lessThanOrEqual":"6.12.*","status":"unaffected","versionType":"semver"},{"version":"6.18.53","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.7","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3-rc2","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":"6.6.158"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.12.111"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.4","versionEndExcluding":"7.3-rc2"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/069d5527bb0f229e528fa88c6b72f15060c373f2"},{"url":"https://git.kernel.org/stable/c/e12c903fd13c6261b98ca18d8f70ac26e739e2f8"},{"url":"https://git.kernel.org/stable/c/74e2a56c82209b0335b53e25f19f9b0590e2483d"},{"url":"https://git.kernel.org/stable/c/71203a41d6fa2fa0ea2f3a7541987958bd3694fd"},{"url":"https://git.kernel.org/stable/c/4aa61c88b4e292e10abdfd791334b8272108d68a"}],"title":"vxlan: mdb: Fix use-after-free in vxlan_mdb_remote_src_del()","x_generator":{"engine":"bippy-1.2.0"}}}}