CVE-2026-99117 (GCVE-0-2026-99117)

Vulnerability from cvelistv5 – Published: 2026-10-28 10:34 – Updated: 2026-10-28 10:34
VLAI
Title
net: bridge: mcast: don't truncate the port group walk on teardown
Summary
In the Linux kernel, the following vulnerability has been resolved: net: bridge: mcast: don't truncate the port group walk on teardown __br_multicast_disable_port_ctx() and br_multicast_del_port() walk port->mglist with hlist_for_each_entry_safe(). However, br_multicast_find_del_pg() can also delete other entries from the same list through br_multicast_fwd_src_remove() or __fwd_del_star_excl(). If such an entry is the iterator's saved next node, hlist_del_init() clears its ->next and terminates the walk early. The reproducer triggers this in both teardown walks, leaving port groups in the bridge mdb with a dangling ->key.port after del_nbp() frees the port: BUG: KASAN: slab-use-after-free in __mdb_fill_info+0x1191/0x1320 __mdb_fill_info+0x1191/0x1320 br_mdb_dump+0x594/0xe40 rtnl_mdb_dump+0x1cf/0x5d0 Use hlist_del_init_rcu() to unlink the group while preserving ->next. br_multicast_del_pg() and the teardown walks run under br->multicast_lock. The GC worker must acquire the same lock before detaching the group for destruction, so the node remains alive while the walk uses the preserved pointer. Preserving ->next means a walk can now reach a group that an earlier iteration already deleted as a side effect. That group is off mp->ports, so br_multicast_find_del_pg() would fall through its port scan and hit the trailing WARN_ON(1). Skip such groups at the top of that helper: a port group is put on port->mglist when it is created and only unlinked when it is deleted, so hlist_unhashed() identifies exactly this case.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7033 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 , < 8243d587a081e790ad96e80d48eef44d9f7ef005 (git)
Affected: b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 , < b45e8c24608c992d1e2cea047eb5bcbfa537f86b (git)
Affected: b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 , < 5a3f7a683aee56e1f15c9d53041f3236767eaae7 (git)
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Linux Linux Affected: 5.10
Unaffected: 0 , < 5.10 (semver)
Unaffected: 6.18.59 , ≤ 6.18.* (semver)
Unaffected: 7.2.13 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
            "net/bridge/br_multicast.c"
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: mcast: don\u0027t truncate the port group walk on teardown\n\n__br_multicast_disable_port_ctx() and br_multicast_del_port() walk\nport-\u003emglist with hlist_for_each_entry_safe(). However,\nbr_multicast_find_del_pg() can also delete other entries from the same\nlist through br_multicast_fwd_src_remove() or __fwd_del_star_excl().\n\nIf such an entry is the iterator\u0027s saved next node, hlist_del_init()\nclears its -\u003enext and terminates the walk early. The reproducer triggers\nthis in both teardown walks, leaving port groups in the bridge mdb with\na dangling -\u003ekey.port after del_nbp() frees the port:\n\n  BUG: KASAN: slab-use-after-free in __mdb_fill_info+0x1191/0x1320\n   __mdb_fill_info+0x1191/0x1320\n   br_mdb_dump+0x594/0xe40\n   rtnl_mdb_dump+0x1cf/0x5d0\n\nUse hlist_del_init_rcu() to unlink the group while preserving -\u003enext.\nbr_multicast_del_pg() and the teardown walks run under\nbr-\u003emulticast_lock. The GC worker must acquire the same lock before\ndetaching the group for destruction, so the node remains alive while\nthe walk uses the preserved pointer.\n\nPreserving -\u003enext means a walk can now reach a group that an earlier\niteration already deleted as a side effect. That group is off mp-\u003eports,\nso br_multicast_find_del_pg() would fall through its port scan and hit\nthe trailing WARN_ON(1). Skip such groups at the top of that helper: a\nport group is put on port-\u003emglist when it is created and only unlinked\nwhen it is deleted, so hlist_unhashed() identifies exactly this case."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-28T10:34:33.874Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/5a3f7a683aee56e1f15c9d53041f3236767eaae7"
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      "title": "net: bridge: mcast: don\u0027t truncate the port group walk on teardown",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-99117",
    "datePublished": "2026-10-28T10:34:33.874Z",
    "dateReserved": "2026-09-25T10:25:14.392Z",
    "dateUpdated": "2026-10-28T10:34:33.874Z",
    "state": "PUBLISHED"
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      "epss": "0.00167",
      "percentile": "0.05901"
    },
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      "cve": "CVE-2026-99117",
      "id": "msrc_CVE-2026-99117",
      "initial_release_date": "2026-10-29T01:04:04.000Z",
      "product_status:known_affected": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "net: bridge: mcast: don\u0027t truncate the port group walk on teardown",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-99117.json",
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          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: mcast: don\u0027t truncate the port group walk on teardown\n\n__br_multicast_disable_port_ctx() and br_multicast_del_port() walk\nport-\u003emglist with hlist_for_each_entry_safe(). However,\nbr_multicast_find_del_pg() can also delete other entries from the same\nlist through br_multicast_fwd_src_remove() or __fwd_del_star_excl().\n\nIf such an entry is the iterator\u0027s saved next node, hlist_del_init()\nclears its -\u003enext and terminates the walk early. The reproducer triggers\nthis in both teardown walks, leaving port groups in the bridge mdb with\na dangling -\u003ekey.port after del_nbp() frees the port:\n\n  BUG: KASAN: slab-use-after-free in __mdb_fill_info+0x1191/0x1320\n   __mdb_fill_info+0x1191/0x1320\n   br_mdb_dump+0x594/0xe40\n   rtnl_mdb_dump+0x1cf/0x5d0\n\nUse hlist_del_init_rcu() to unlink the group while preserving -\u003enext.\nbr_multicast_del_pg() and the teardown walks run under\nbr-\u003emulticast_lock. The GC worker must acquire the same lock before\ndetaching the group for destruction, so the node remains alive while\nthe walk uses the preserved pointer.\n\nPreserving -\u003enext means a walk can now reach a group that an earlier\niteration already deleted as a side effect. That group is off mp-\u003eports,\nso br_multicast_find_del_pg() would fall through its port scan and hit\nthe trailing WARN_ON(1). Skip such groups at the top of that helper: a\nport group is put on port-\u003emglist when it is created and only unlinked\nwhen it is deleted, so hlist_unhashed() identifies exactly this case."
          }
        ],
        "id": "CVE-2026-99117",
        "lastModified": "2026-10-28T11:17:31.253",
        "metrics": {},
        "published": "2026-10-28T11:17:31.253",
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      "cve": "CVE-2026-99117",
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      "product_status:known_affected": "250",
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      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net: bridge: mcast: don\u0027t truncate the port group walk on teardown",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-99117.json",
      "version": "3"
    }
  }
}



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