CVE-2026-90078: In the Linux kernel, the following vulnerability has been resolved: net/sched: act_skbmod: fix length calculations and avoid invalid header warnings syzbot re

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_skbmod: fix length calculations and avoid invalid header warnings syzbot re

In the Linux kernel, the following vulnerability has been resolved: net/sched: act_skbmod: fix length calculations and avoid invalid header warnings syzbot reported a warning in skb_network_header_len() triggered by tcf_skbmod_act(): !skb_transport_header_was_set(skb) WARNING: CPU: 0 PID: 14949 at include/linux/skbuff.h:3243 skb_network_header_len include/linux/skbuff.h:3243 [inline] WARNING: CPU: 0 PID: 14949 at net/sched/act_skbmod.c:55 tcf_skbmod_act+0xfe8/0x1810 net/sched/act_skbmod.c:55 There are a few issues in tcf_skbmod_act(): 1. Calling skb_network_header_len() assumes skb->transport_header is set, which is not guaranteed when tcf_skbmod_act() runs at TC ingress. 2. Unconditionally calling skb_mac_header_len() at the beginning of tcf_skbmod_act() triggers a warning on L3 devices (e.g. TUN) where the MAC header is unset, evaluating to an underflowed garbage length. 3. On TC ingress, skb->data points to the network header. Adding the MAC header length to the IP header length causes skb_ensure_writable() to request more bytes than the actual IP packet length, dropping valid short packets (e.g. 28-byte UDP/IPv4 packets). Fix these by: - Using skb_

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 0.21%, higher than 11% 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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