CVE Catalog

CVE-2025-40297

HighCVSS 7.8
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Low risk
0.14%

4th percentile - higher than 4% of all known CVEs

Summary

In the Linux kernel's network bridging subsystem (net/bridge), a use-after-free was found when deleting an expired FDB entry. The issue is due to a race condition between FDB learning and port deletion when MST is enabled and VLAN filtering is disabled. MST bypasses the port state, allowing FDB learning at an inappropriate time.

Risk Assessment

An attacker could exploit this bug to access already freed memory, potentially leading to system crash or code execution in kernel context.

Recommendation

It is recommended to update the Linux kernel to a version containing the fix that adds a check for the port's VLAN group pointer to prevent MST from bypassing the port state.

Other vulnerabilities in Linux kernel

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Original NVD description (English source)

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

Vulnerability data from NVD (NIST) · CISA KEV · EPSS