In the Linux kernel, the following vulnerability has been resolved:
vxlan: mdb: Fix use-after-free in vxlan_mdb_remote_src_del()
vxlan_mdb_is_valid_source(), which validates MDBE_ATTR_SOURCE and every
MDBE_ATTR_SRC_LIST member, accepts the all-zeros address.
A source list is only accepted on a (*, G) entry, whose source is the
all-zeros address, and for each member of the list an (S, G) entry is
derived from it by substituting the source. Entries are keyed by a plain
memcmp() of struct vxlan_mdb_entry_key, so if MDBE_ATTR_SOURCE is present
and holds the all-zeros address and the source list holds it as well, the
derived (S, G) key is byte-identical to the (*, G) key and resolves to the
same entry. Omitting MDBE_ATTR_SOURCE is not equivalent, as the key is
then left with a zero address family.
vxlan_mdb_remote_src_del() removes the forwarding entry of a source before
freeing the source entry:
vxlan_mdb_remote_src_fwd_del(vxlan, group, remote, &ent->addr);
vxlan_mdb_remote_src_entry_del(ent);
With the keys aliased, the first call deletes the remote of the entry that
owns 'ent' instead of a separate (S, G) entry, and frees 'ent'. The second
call then runs on the freed entry, and its hlist_del() reads ->pprev and
->next out of it and writes through them.
Adding the (*, G) entry with NLM_F_REPLACE and no source list marks the
all-zeros source for deletion and reaches this from the sweep at the end
of vxlan_mdb_remote_srcs_replace().
BUG: KASAN: slab-use-after-free in __vxlan_mdb_add+0x1cd/0xd70
Read of size 8 at addr ffff888102852500 by task poc/84
__vxlan_mdb_add+0x1cd/0xd70
vxlan_mdb_add+0xc0/0x140
rtnl_mdb_add+0x157/0x2a0
rtnetlink_rcv_msg+0x207/0x5a0
Allocated by task 84:
__kmalloc_cache_noprof+0x153/0x360
vxlan_mdb_remote_srcs_add+0x2eb/0x440
__vxlan_mdb_add+0x803/0xd70
Freed by task 84:
kfree+0x14c/0x3b0
vxlan_mdb_remote_del+0x129/0x1a0
__vxlan_mdb_del+0x4f/0xe0
vxlan_mdb_remote_src_fwd_del.isra.0+0x162/0x1b0
__vxlan_mdb_add+0x1c5/0xd70
The MDB operations are netns-scoped, so an unprivileged user can perform
them in a new user and network namespace.
Reject the all-zeros address in vxlan_mdb_is_valid_source(), which covers
both call sites. A (*, G) entry is expressed by omitting the source, so
nothing legitimate is refused.
Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>
References
Configurations
Configuration 1 (hide)
|
History
22 Oct 2026, 17:12
| Type | Values Removed | Values Added |
|---|---|---|
| First Time |
Linux linux Kernel
Linux |
|
| CWE | CWE-416 | |
| CPE | cpe:2.3:o:linux:linux_kernel:7.3:rc1:*:*:*:*:*:* cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
|
| References | () https://git.kernel.org/stable/c/069d5527bb0f229e528fa88c6b72f15060c373f2 - Patch | |
| References | () https://git.kernel.org/stable/c/4aa61c88b4e292e10abdfd791334b8272108d68a - Patch | |
| References | () https://git.kernel.org/stable/c/71203a41d6fa2fa0ea2f3a7541987958bd3694fd - Patch | |
| References | () https://git.kernel.org/stable/c/74e2a56c82209b0335b53e25f19f9b0590e2483d - Patch | |
| References | () https://git.kernel.org/stable/c/e12c903fd13c6261b98ca18d8f70ac26e739e2f8 - Patch |
03 Oct 2026, 11:18
| Type | Values Removed | Values Added |
|---|---|---|
| References |
|
25 Sep 2026, 15:18
| Type | Values Removed | Values Added |
|---|---|---|
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 7.8 |
25 Sep 2026, 11:17
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-09-25 11:17
Updated : 2026-10-22 17:19
NVD link : CVE-2026-98122
Mitre link : CVE-2026-98122
CVE.ORG link : CVE-2026-98122
JSON object : View
Products Affected
linux
- linux_kernel
CWE
CWE-416
Use After Free