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GHSA-PHHG-87VX-7J2V

Vulnerability from github – Published: 2026-10-28 12:31 – Updated: 2026-10-28 12:31

Details

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.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-99117"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-28T11:17:31Z",
    "severity": null
  },
  "details": "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": "GHSA-phhg-87vx-7j2v",
  "modified": "2026-10-28T12:31:03Z",
  "published": "2026-10-28T12:31:03Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99117"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5a3f7a683aee56e1f15c9d53041f3236767eaae7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8243d587a081e790ad96e80d48eef44d9f7ef005"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/b45e8c24608c992d1e2cea047eb5bcbfa537f86b"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

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

Vulnerability from cvelistv5 – Published: 2026-10-28 10:34 – Updated: 2026-10-28 10:34

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

3 references

URL	Tags
https://git.kernel.org/stable/c/8243d587a081e790a…
https://git.kernel.org/stable/c/b45e8c24608c992d1…
https://git.kernel.org/stable/c/5a3f7a683aee56e1f…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 , < 8243d587a081e790ad96e80d48eef44d9f7ef005 (git) Affected: b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 , < b45e8c24608c992d1e2cea047eb5bcbfa537f86b (git) Affected: b08123684bd55fa6d6ee4b52d4ae3040fadb5aa2 , < 5a3f7a683aee56e1f15c9d53041f3236767eaae7 (git)
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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          "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."
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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