CVE-2026-98487 (GCVE-0-2026-98487)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:16 – Updated: 2026-10-24 14:09
VLAI
Title
net: bridge: mdb: restart port group walk after deletion
Summary
In the Linux kernel, the following vulnerability has been resolved: net: bridge: mdb: restart port group walk after deletion br_mdb_flush_pgs() keeps a pointer-to-pointer cursor while walking mp->ports. br_multicast_del_pg() can re-enter the same MDB entry through br_multicast_sg_del_exclude_ports() and unlink other port groups. If the cursor points into one of those groups, the next iteration dereferences a stale cursor and can leave mp->ports pointing at freed memory. A following RTM_GETMDB exposes the dangling pointer: BUG: KASAN: slab-use-after-free in br_mdb_dump Read of size 8 br_mdb_dump rtnl_mdb_dump rtnl_dumpit netlink_dump Reset the cursor to mp->ports after every deletion. The deletion removes at least the selected group, so the restarted walk always makes progress.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6971 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: a6acb535afb2a3b688a7858f05b61f0433e480d5 , < 46ec55855c972504258c371677ac039ba20e5d12 (git)
Affected: a6acb535afb2a3b688a7858f05b61f0433e480d5 , < ab3c4a4c85f2e1e8d04b5c1770dea8412d21c7fe (git)
Affected: a6acb535afb2a3b688a7858f05b61f0433e480d5 , < fe2a42789c12eb7c5d3a42191e2cc735a6c35ead (git)
Affected: a6acb535afb2a3b688a7858f05b61f0433e480d5 , < ab1404ac81154a89fb61ac50ae9a04cd8d4834dc (git)
guessed Create a notification for this product.
Linux Linux Affected: 6.8
Unaffected: 0 , < 6.8 (semver)
Unaffected: 6.12.112 , ≤ 6.12.* (semver)
Unaffected: 6.18.55 , ≤ 6.18.* (semver)
Unaffected: 7.2.9 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: mdb: restart port group walk after deletion\n\nbr_mdb_flush_pgs() keeps a pointer-to-pointer cursor while walking\nmp-\u003eports. br_multicast_del_pg() can re-enter the same MDB entry through\nbr_multicast_sg_del_exclude_ports() and unlink other port groups. If the\ncursor points into one of those groups, the next iteration dereferences a\nstale cursor and can leave mp-\u003eports pointing at freed memory.\n\nA following RTM_GETMDB exposes the dangling pointer:\n\n  BUG: KASAN: slab-use-after-free in br_mdb_dump\n  Read of size 8\n    br_mdb_dump\n    rtnl_mdb_dump\n    rtnl_dumpit\n    netlink_dump\n\nReset the cursor to mp-\u003eports after every deletion. The deletion removes at\nleast the selected group, so the restarted walk always makes progress."
        }
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              "value": "AV:L - A local sendmsg() on NETLINK_ROUTE carrying RTM_DELMDB with NLM_F_BULK reaches the patched br_mdb_flush_pgs() through rtnl_mdb_del() and ndo_mdb_del_bulk; received bridge packets do not enter this bulk-delete path.\nAC:L - The attacker can add a *,G EXCLUDE membership and permanent static S,G groups so br_multicast_sg_add_exclude_ports() creates skipped kernel-protocol STAR_EXCL nodes; a proto-static bulk flush then deterministically invalidates pp without a race.\nPR:L - rtnetlink_rcv_msg() requires CAP_NET_ADMIN through netlink_net_capable(), but an unprivileged user can obtain that capability in a user-created network namespace and create the bridge, ports, and MDB state there.\nUI:N - The attacker performs the RTM_NEWMDB setup, NLM_F_BULK RTM_DELMDB trigger, and optional RTM_GETMDB traversal through their own netlink socket; no victim action is required.\nS:U - The dangling mp-\u003eports pointer corrupts and exposes bridge objects within the host kernel\u0027s existing security authority; it does not cross a guest-host, hypervisor, or IOMMU boundary.\nC:H - The persistent slab UAF lets reclaimed contents control p-\u003enext and p-\u003ekey.port; br_mdb_fill_info() follows these links and returns port, timer, flag, and source-list data through RTM_GETMDB, enabling kernel-memory disclosure.\nI:H - Reusing the dangling node in br_multicast_del_pg() reaches hlist_del_init_rcu() through reclaimed pg-\u003emglist.pprev and updates rhashtable and GC links, providing attacker-influenced kernel writes and potential control-flow hijacking.\nA:H - After br_multicast_destroy_port_group() calls kfree_rcu(), br_mdb_dump() produces the confirmed slab-use-after-free; stale p-\u003ekey.port or p-\u003enext dereferences in dump or br_multicast_flood can oops or panic the kernel."
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    "datePublished": "2026-10-18T15:16:04.746Z",
    "dateReserved": "2026-09-25T10:25:14.352Z",
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    "state": "PUBLISHED"
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          }
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        "lastModified": "2026-10-24T14:16:43.960",
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}



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