CVE-2025-39874

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

macsec: sync features on RTM_NEWLINK

Syzkaller managed to lock the lower device via ETHTOOL_SFEATURES:

netdev_lock include/linux/netdevice.h:2761 [inline]

netdev_lock_ops include/net/netdev_lock.h:42 [inline]

netdev_sync_lower_features net/core/dev.c:10649 [inline]

__netdev_update_features+0xcb1/0x1be0 net/core/dev.c:10819

netdev_update_features+0x6d/0xe0 net/core/dev.c:10876

macsec_notify+0x2f5/0x660 drivers/net/macsec.c:4533

notifier_call_chain+0x1b3/0x3e0 kernel/notifier.c:85

call_netdevice_notifiers_extack net/core/dev.c:2267 [inline]

call_netdevice_notifiers net/core/dev.c:2281 [inline]

netdev_features_change+0x85/0xc0 net/core/dev.c:1570

__dev_ethtool net/ethtool/ioctl.c:3469 [inline]

dev_ethtool+0x1536/0x19b0 net/ethtool/ioctl.c:3502

dev_ioctl+0x392/0x1150 net/core/dev_ioctl.c:759

It happens because lower features are out of sync with the upper:

__dev_ethtool (real_dev)

netdev_lock_ops(re

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References