CVE-2026-98301

net: bridge: mst: move switchdev call outside rcu

Published Oct 6, 2026 CVSS 3.1 · 7.0 High EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

net: bridge: mst: move switchdev call outside rcu

This is a follow-up of one of sashiko's pre-existing bug reports.
br_mst_set_state() calls switchdev_port_attr_set() for nonzero MSTIs
while holding rcu_read_lock() which invokes the blocking switchdev
notifier chain and may sleep. Nonzero MSTI changes come from netlink
with rtnl held. Move the switchdev call before entering the rcu section and
assert that rtnl is held.

The call cannot be deferred because netlink needs its error and extack.
Also DSA reads the old bridge MST state during the callback and checks it.
A deferred callback will be late and will see the updated state.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4841-1 linux security update
Debian DLA Debian DLA DLA-4850-1 linux-6.12 security update
Debian DSA Debian DSA DSA-6568-1 linux security update
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9022-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9023-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9024-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9025-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9026-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9039-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-9040-1 Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9066-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-9091-1 Linux kernel (NVIDIA Tegra) vulnerabilities
History
Type Values Removed Values Added
Weaknesses CWE-727
Type Values Removed Values Added
Weaknesses CWE-821
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Moderate

Type Values Removed Values Added
Weaknesses CWE-727
Type Values Removed Values Added
Weaknesses CWE-236
CWE-667
Type Values Removed Values Added
Weaknesses CWE-236
CWE-667
Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: net: bridge: mst: move switchdev call outside rcu This is a follow-up of one of sashiko's pre-existing bug reports. br_mst_set_state() calls switchdev_port_attr_set() for nonzero MSTIs while holding rcu_read_lock() which invokes the blocking switchdev notifier chain and may sleep. Nonzero MSTI changes come from netlink with rtnl held. Move the switchdev call before entering the rcu section and assert that rtnl is held. The call cannot be deferred because netlink needs its error and extack. Also DSA reads the old bridge MST state during the callback and checks it. A deferred callback will be late and will see the updated state.
Title net: bridge: mst: move switchdev call outside rcu
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 19, 2026, 9:17 AM
Reserved
Sep 25, 2026, 10:25 AM
Status
Received
Published
Oct 6, 2026, 9:18 AM
Modified
Oct 19, 2026, 10:18 AM
Severity
Moderate
Public date
Oct 6, 2026, 12:00 AM