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CVE-2026-31421

net/sched: cls_fw: fix NULL pointer dereference on shared blocks

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, and 2 more
None on Exploit-DB, Metasploit or GitHub

Summary

In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_fw: fix NULL pointer dereference on shared blocks The old-method path in fw_classify() calls tcf_block_q() and dereferences q->handle. Shared blocks leave block->q NULL, causing a NULL deref when an empty cls_fw filter is attached to a shared block and a packet with a nonzero major skb mark is classified. Reject the configuration in fw_change() when the old method (no TCA_OPTIONS) is used on a shared block, since fw_classify()'s old-method path needs block->q which is NULL for shared blocks. The fixed null-ptr-deref calling stack: KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] RIP: 0010:fw_classify (net/sched/cls_fw.c:81) Call Trace: tcf_classify (./include/net/tc_wrapper.h:197 net/sched/cls_api.c:1764 net/sched/cls_api.c:1860) tc_run (net/core/dev.c:4401) __dev_queue_xmit (net/core/dev.c:4535 net/core/dev.c:4790)

Timeline

  1. CVE published
  2. Record last updated

Affected versions

  • Linux Linux

    From 1abf272022cf1d18469405f47b4ec49c6a3125db · fixed in d6d5bd62a09650856e1e2010eb09853eba0d64e1; From 1abf272022cf1d18469405f47b4ec49c6a3125db · fixed in febf64ca79a2d6540ab6e5e197fa0f4f7e84473e; From 1abf272022cf1d18469405f47b4ec49c6a3125db · fixed in 3d41f9a314afa94b1c7c7c75405920123220e8cd; From 1abf272022cf1d18469405f47b4ec49c6a3125db · fixed in 18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28; From 1abf272022cf1d18469405f47b4ec49c6a3125db · fixed in 5cf41031922c154aa5ccda8bcdb0f5e6226582ec; From 1abf272022cf1d18469405f47b4ec49c6a3125db · fixed in 3cb055df9e8625ce699a259d8178d67b37f2b160; From 1abf272022cf1d18469405f47b4ec49c6a3125db · fixed in 96426c348def662b06bfdc65be3002905604927a; From 1abf272022cf1d18469405f47b4ec49c6a3125db · fixed in faeea8bbf6e958bf3c00cb08263109661975987c

  • Linux Linux

    4.15

  • KernelLinux

    From 4.15.0 · fixed in 5.10.253; From 5.11.0 · fixed in 5.15.203; From 5.16.0 · fixed in 6.1.168; From 6.2.0 · fixed in 6.6.134; From 6.7.0 · fixed in 6.12.81; From 6.13.0 · fixed in 6.18.22; From 6.19.0 · fixed in 6.19.12

References 8

git.kernel.org