CVE-2025-40297 (GCVE-0-2025-40297)

Vulnerability from cvelistv5 – Published: 2025-12-08 00:46 – Updated: 2025-12-08 00:46
VLAI?
Summary
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 being deleted. VLAN filtering must be disabled because we flush the port VLANs when it's being deleted which will stop learning. This fix adds a check for the port's vlan group which is initialized to NULL when the port is getting deleted, that avoids the port state bypass. When MST is enabled there would be a minimal new overhead in the fast-path because the port's vlan group pointer is cache-hot. [1] https://syzkaller.appspot.com/bug?extid=dd280197f0f7ab3917be
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: ec7328b59176227216c461601c6bd0e922232a9b , < e19085b2a86addccff33ab8536fc67ebd9d52198 (git)
Affected: ec7328b59176227216c461601c6bd0e922232a9b , < 3b60ce334c1ce8b3fad7e02dcd5ed9f6646477c8 (git)
Affected: ec7328b59176227216c461601c6bd0e922232a9b , < bf3843183bc3158e5821b46f330c438ae9bd6ddb (git)
Affected: ec7328b59176227216c461601c6bd0e922232a9b , < 991fbe1680cd41a5f97c92cd3a3496315df36e4b (git)
Affected: ec7328b59176227216c461601c6bd0e922232a9b , < 8dca36978aa80bab9d4da130c211db75c9e00048 (git)
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    Linux Linux Affected: 5.18
Unaffected: 0 , < 5.18 (semver)
Unaffected: 6.1.159 , ≤ 6.1.* (semver)
Unaffected: 6.6.117 , ≤ 6.6.* (semver)
Unaffected: 6.12.58 , ≤ 6.12.* (semver)
Unaffected: 6.17.8 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bridge: fix use-after-free due to MST port state bypass\n\nsyzbot reported[1] a use-after-free when deleting an expired fdb. It is\ndue to a race condition between learning still happening and a port being\ndeleted, after all its fdbs have been flushed. The port\u0027s state has been\ntoggled to disabled so no learning should happen at that time, but if we\nhave MST enabled, it will bypass the port\u0027s state, that together with VLAN\nfiltering disabled can lead to fdb learning at a time when it shouldn\u0027t\nhappen while the port is being deleted. VLAN filtering must be disabled\nbecause we flush the port VLANs when it\u0027s being deleted which will stop\nlearning. This fix adds a check for the port\u0027s vlan group which is\ninitialized to NULL when the port is getting deleted, that avoids the port\nstate bypass. When MST is enabled there would be a minimal new overhead\nin the fast-path because the port\u0027s vlan group pointer is cache-hot.\n\n[1] https://syzkaller.appspot.com/bug?extid=dd280197f0f7ab3917be"
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          "url": "https://git.kernel.org/stable/c/8dca36978aa80bab9d4da130c211db75c9e00048"
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    "dateReserved": "2025-04-16T07:20:57.185Z",
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}


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  • 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.
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