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vuln-cve/data/2026/98xxx/CVE-2026-98122.json
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{
"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": "2026-10-19T09:14:14.316Z"
},
"containers": {
"cna": {
"providerMetadata": {
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux",
"dateUpdated": "2026-10-19T09:14:14.316Z"
},
"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",
"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"
}
]
}
]
}
],
"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"
}
}
}
}
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