CVE-2026-31421 (GCVE-0-2026-31421)
Vulnerability from cvelistv5
Published
2026-04-13 13:40
Modified
2026-04-13 13:40
Severity ?
VLAI Severity ?
EPSS score ?
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)
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 1abf272022cf1d18469405f47b4ec49c6a3125db Version: 1abf272022cf1d18469405f47b4ec49c6a3125db Version: 1abf272022cf1d18469405f47b4ec49c6a3125db Version: 1abf272022cf1d18469405f47b4ec49c6a3125db Version: 1abf272022cf1d18469405f47b4ec49c6a3125db Version: 1abf272022cf1d18469405f47b4ec49c6a3125db |
||
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"descriptions": [
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"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_fw: fix NULL pointer dereference on shared blocks\n\nThe old-method path in fw_classify() calls tcf_block_q() and\ndereferences q-\u003ehandle. Shared blocks leave block-\u003eq NULL, causing a\nNULL deref when an empty cls_fw filter is attached to a shared block\nand a packet with a nonzero major skb mark is classified.\n\nReject the configuration in fw_change() when the old method (no\nTCA_OPTIONS) is used on a shared block, since fw_classify()\u0027s\nold-method path needs block-\u003eq which is NULL for shared blocks.\n\nThe fixed null-ptr-deref calling stack:\n KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]\n RIP: 0010:fw_classify (net/sched/cls_fw.c:81)\n Call Trace:\n tcf_classify (./include/net/tc_wrapper.h:197 net/sched/cls_api.c:1764 net/sched/cls_api.c:1860)\n tc_run (net/core/dev.c:4401)\n __dev_queue_xmit (net/core/dev.c:4535 net/core/dev.c:4790)"
}
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"providerMetadata": {
"dateUpdated": "2026-04-13T13:40:25.278Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
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"references": [
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{
"url": "https://git.kernel.org/stable/c/18328eff2f97d1a6adcdb6d4a0f42f2f83a31e28"
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{
"url": "https://git.kernel.org/stable/c/5cf41031922c154aa5ccda8bcdb0f5e6226582ec"
},
{
"url": "https://git.kernel.org/stable/c/3cb055df9e8625ce699a259d8178d67b37f2b160"
},
{
"url": "https://git.kernel.org/stable/c/96426c348def662b06bfdc65be3002905604927a"
},
{
"url": "https://git.kernel.org/stable/c/faeea8bbf6e958bf3c00cb08263109661975987c"
}
],
"title": "net/sched: cls_fw: fix NULL pointer dereference on shared blocks",
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"cveId": "CVE-2026-31421",
"datePublished": "2026-04-13T13:40:25.278Z",
"dateReserved": "2026-03-09T15:48:24.088Z",
"dateUpdated": "2026-04-13T13:40:25.278Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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