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CVE-2026-90078

net/sched: act_skbmod: fix length calculations and avoid invalid header warnings

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.15.221, 6.1.188, 6.6.157, 6.12.110, 6.18.52, and 1 more
None on Exploit-DB, Metasploit or GitHub

Summary

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_network_offset(skb) + sizeof(struct iphdr/ipv6hdr) for SKBMOD_F_ECN so that the required length is correctly calculated on both ingress (offset == 0) and egress (offset == mac_len). • Setting max_edit_len to ETH_HLEN for Ethernet header modifications after validating ARPHRD_ETHER.

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 56af5e749f20c3a540310c207dcc373f4f09156e · fixed in 985a37781ade19061400100c2ba0f43979dd4d63; From 56af5e749f20c3a540310c207dcc373f4f09156e · fixed in d896843d8d925f0adbba319020595cfb1a7bcd57; From 56af5e749f20c3a540310c207dcc373f4f09156e · fixed in 0675cff3c2924eb9b80d9dd250cf56a1140af157; From 56af5e749f20c3a540310c207dcc373f4f09156e · fixed in e8a2027b7e686784a69b2dfcee841d779919f313; From 56af5e749f20c3a540310c207dcc373f4f09156e · fixed in 1719865b20b22c88d2a55e922eff5ca31b0841f6; From 56af5e749f20c3a540310c207dcc373f4f09156e · fixed in 62126464f3a6159c0a3dd89e196ba65bfeb0afc6; From 56af5e749f20c3a540310c207dcc373f4f09156e · fixed in 81d0d1e64f30d9989c829c0953cd6e6c68d9c5fb

  • Linux Linux

    5.15

  • KernelLinux

    From 5.15.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.188; From 6.2.0 · fixed in 6.6.157; From 6.7.0 · fixed in 6.12.110; From 6.13.0 · fixed in 6.18.52; From 6.19.0 · fixed in 7.2.6

References 7

git.kernel.org