net/sched: cls_fw: fix NULL pointer dereference on shared blocks
Summary
| CVE | CVE-2026-31421 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-04-13 14:16:11 UTC |
| Updated | 2026-04-18 09:16:31 UTC |
| Description | 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) |
Risk And Classification
EPSS: 0.000240000 probability, percentile 0.066100000 (date 2026-04-18)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 1abf272022cf1d18469405f47b4ec49c6a3125db d6d5bd62a09650856e1e2010eb09853eba0d64e1 git | Not specified |
| CNA | Linux | Linux | affected 1abf272022cf1d18469405f47b4ec49c6a3125db febf64ca79a2d6540ab6e5e197fa0f4f7e84473e git | Not specified |
| CNA | Linux | Linux | affected 1abf272022cf1d18469405f47b4ec49c6a3125db 3d41f9a314afa94b1c7c7c75405920123220e8cd git | Not specified |
| CNA | Linux | Linux | affected 1abf272022cf1d18469405f47b4ec49c6a3125db 18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28 git | Not specified |
| CNA | Linux | Linux | affected 1abf272022cf1d18469405f47b4ec49c6a3125db 5cf41031922c154aa5ccda8bcdb0f5e6226582ec git | Not specified |
| CNA | Linux | Linux | affected 1abf272022cf1d18469405f47b4ec49c6a3125db 3cb055df9e8625ce699a259d8178d67b37f2b160 git | Not specified |
| CNA | Linux | Linux | affected 1abf272022cf1d18469405f47b4ec49c6a3125db 96426c348def662b06bfdc65be3002905604927a git | Not specified |
| CNA | Linux | Linux | affected 1abf272022cf1d18469405f47b4ec49c6a3125db faeea8bbf6e958bf3c00cb08263109661975987c git | Not specified |
| CNA | Linux | Linux | affected 4.15 | Not specified |
| CNA | Linux | Linux | unaffected 4.15 semver | Not specified |
| CNA | Linux | Linux | unaffected 5.10.253 5.10.* semver | Not specified |
| CNA | Linux | Linux | unaffected 5.15.203 5.15.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.1.168 6.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.6.134 6.6.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.12.81 6.12.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.18.22 6.18.* semver | Not specified |
| CNA | Linux | Linux | unaffected 6.19.12 6.19.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.0 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/d6d5bd62a09650856e1e2010eb09853eba0d64e1 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/faeea8bbf6e958bf3c00cb08263109661975987c | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/3d41f9a314afa94b1c7c7c75405920123220e8cd | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/3cb055df9e8625ce699a259d8178d67b37f2b160 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/febf64ca79a2d6540ab6e5e197fa0f4f7e84473e | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/5cf41031922c154aa5ccda8bcdb0f5e6226582ec | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/96426c348def662b06bfdc65be3002905604927a | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.