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Review reviewHigh

CVE-2025-40297

Linux

In the Linux kernel, the following vulnerability has been resolved: net: bridge: fix use-after-free due to MST port state bypass syzbot reported[1] a use-after-free when deleting an expired fdb. It is due to a race condition between learning still happening and a port being deleted, after all its fdbs have been flushed. The port's state has been toggled to disabled so no learning should happen at that time, but if we have MST enabled, it will bypass the port's state, that together with VLAN filtering disabled can lead to fdb learning at a time when it shouldn't happen while the port is bein...

CVSS
7.8
EPSS
-
- percentile
CISA KEV
Not listed
Published
2025.12.08
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 7.8

Vulnerability overview

In the Linux kernel, the following vulnerability has been resolved: net: bridge: fix use-after-free due to MST port state bypass syzbot reported[1] a use-after-free when deleting an expired fdb. It is due to a race condition between learning still happening and a port being deleted, after all its fdbs have been flushed. The port's state has been toggled to disabled so no learning should happen at that time, but if we have MST enabled, it will bypass the port's state, that together with VLAN filtering disabled can lead to fdb learning at a time when it shouldn't happen while the port is bein...

Affected product and versions

Product
Linux
Affected versions
>= ec7328b59176227216c461601c6bd0e922232a9b < e19085b2a86addccff33ab8536fc67ebd9d52198, >= ec7328b59176227216c461601c6bd0e922232a9b < 3b60ce334c1ce8b3fad7e02dcd5ed9f6646477c8, >= ec7328b59176227216c461601c6bd0e922232a9b < bf3843183bc3158e5821b46f330c438ae9bd6ddb, >= ec7328b59176227216c461601c6bd0e922232a9b < 991fbe1680cd41a5f97c92cd3a3496315df36e4b, >= ec7328b59176227216c461601c6bd0e922232a9b < 8dca36978aa80bab9d4da130c211db75c9e00048, >= 5.18
Fixed versions
No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE
Not available