CVE-2025-39874: In the Linux kernel, the following vulnerability has been resolved: macsec: sync features on RTM_NEWLINK Syzkaller managed to lock the lower device via ETHTOO

In the Linux kernel, the following vulnerability has been resolved: macsec: sync features on RTM_NEWLINK Syzkaller managed to lock the lower device via ETHTOO

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(real_dev) ETHTOOL_SFEATURES __netdev_features_change netdev_sync_upper_features disable LRO on the lower if (old_features != dev->features) netdev_features_change

Description from the National Vulnerability Database, published by 416baaa9-dc9f-4396-8d5f-8c081fb06d67

What it means for a small business

Linux is on the computers, phones or browsers your team uses every day. Turn on automatic updates and restart: most of these fixes only take effect after a restart.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.13%, higher than 2% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 29, 2026, updated daily.

Check your own setup

Website check: reads what your site runs from the outside (WordPress version, plugins it can see, old server software) and matches it against this database.
Server check: what your web server says about itself, and whether that version has known flaws.

Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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