Описание
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.
A flaw was found in the Linux kernel's network bridge subsystem. When deleting multicast database (MDB) port groups, the kernel can maintain a stale reference to memory that has already been freed during recursive group removal, resulting in a use-after-free condition. A local attacker could exploit this vulnerability through bridge management operations to trigger a system crash, leading to a Denial of Service (DoS), or potentially achieve privilege escalation.
Отчет
A use after free in the bridge MDB control path can occur because br_mdb_flush_pgs keeps a pointer to pointer cursor while br_multicast_del_pg can reenter the same MDB entry and remove additional port groups. If the cursor points into one of the deleted groups, the next iteration dereferences freed memory and mp ports may retain a dangling list pointer. A following local RTM_GETMDB request can reach the stale pointer in br_mdb_dump and cause a kernel crash. For the CVSS the PR:L reflects that triggering requires local MDB management access, commonly through CAP_NET_ADMIN in a network namespace or a delegated container context. The issue is not directly reachable through ordinary remote bridge traffic because the demonstrated trigger uses the local netlink control plane. Impact is at least denial of service through a kernel crash.
Меры по смягчению последствий
Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 10 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 6 | kernel | Out of support scope | ||
| Red Hat Enterprise Linux 7 | kernel | Not affected | ||
| Red Hat Enterprise Linux 7 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel | Not affected | ||
| Red Hat Enterprise Linux 8 | kernel-rt | Not affected | ||
| Red Hat Enterprise Linux 9 | kernel | Fix deferred | ||
| Red Hat Enterprise Linux 9 | kernel-rt | Not affected | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-8 | Not affected | ||
| Red Hat OpenShift Container Platform 4 | openshift/ose-rhel-coreos-9 | Fix deferred |
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Дополнительная информация
Статус:
EPSS
5.5 Medium
CVSS3
Связанные уязвимости
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.
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.
In the Linux kernel, the following vulnerability has been resolved: n ...
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.
EPSS
5.5 Medium
CVSS3