net/sched: cls_flow: fix NULL pointer dereference on shared blocks
In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_flow: fix NULL pointer dereference on shared blocks flow_change() calls tcf_block_q() and dereferences q->handle to derive a default baseclass. Shared blocks leave block->q NULL, causing a NULL deref when a flow filter without a fully qualified baseclass is created on a shared block. Check tcf_block_shared() before accessing block->q and return -EINVAL for shared blocks. This avoids the null-deref shown below: ======================================================================= KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] RIP: 0010:flow_change (net/sched/cls_flow.c:508) Call Trace: tc_new_tfilter (net/sched/cls_api.c:2432) rtnetlink_rcv_msg (net/core/rtnetlink.c:6980) [...] =======================================================================
- Products
- Kernel
- Affected versions
- Not specified
- Fixed versions
- 5.10.253, 5.15.203, 6.1.168, 6.12.81, 6.18.22, 6.19.12, 6.6.134
- CVEs
- CVE-2026-31422
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 10:33 UTC · Revision 1
Source evidence
net/sched: cls_flow: fix NULL pointer dereference on shared blocks
core-osv · Original sourcePublished 13 Apr 2026, 13:40 UTC
In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_flow: fix NULL pointer dereference on shared blocks flow_change() calls tcf_block_q() and dereferences q->handle to derive a default baseclass. Shared blocks leave block->q NULL, causing a NULL deref when a flow filter without a fully qualified baseclass is created on a shared block. Check tcf_block_shared() before accessing block->q and return -EINVAL for shared blocks. This avoids the null-deref shown below: ======================================================================= KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] RIP: 0010:flow_change (net/sched/cls_flow.c:508) Call Trace: tc_new_tfilter (net/sched/cls_api.c:2432) rtnetlink_rcv_msg (net/core/rtnetlink.c:6980) [...] =======================================================================
osv:CVE-2026-31422
Kernel
Fixed versions: 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12
Complete source record
{
"id": "44d3db0d3da8e09a61514898df962423a689f3f32599079e484091083d48b57f",
"url": "https://osv.dev/vulnerability/CVE-2026-31422",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "net/sched: cls_flow: fix NULL pointer dereference on shared blocks",
"summary": "In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_flow: fix NULL pointer dereference on shared blocks flow_change() calls tcf_block_q() and dereferences q->handle to derive a default baseclass. Shared blocks leave block->q NULL, causing a NULL deref when a flow filter without a fully qualified baseclass is created on a shared block. Check tcf_block_shared() before accessing block->q and return -EINVAL for shared blocks. This avoids the null-deref shown below: ======================================================================= KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f] RIP: 0010:flow_change (net/sched/cls_flow.c:508) Call Trace: tc_new_tfilter (net/sched/cls_api.c:2432) rtnetlink_rcv_msg (net/core/rtnetlink.c:6980) [...] =======================================================================",
"evidence": "osv:CVE-2026-31422",
"products": [
{
"name": {
"value": "Kernel",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "5.10.253",
"evidence": "/affected/1/ranges"
},
{
"value": "5.15.203",
"evidence": "/affected/1/ranges"
},
{
"value": "6.1.168",
"evidence": "/affected/1/ranges"
},
{
"value": "6.6.134",
"evidence": "/affected/1/ranges"
},
{
"value": "6.12.81",
"evidence": "/affected/1/ranges"
},
{
"value": "6.18.22",
"evidence": "/affected/1/ranges"
},
{
"value": "6.19.12",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": []
}
],
"severity": "unknown",
"structured": {
"id": "CVE-2026-31422",
"aliases": [
"CVE-2026-31422"
],
"affected": [
{
"ranges": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"type": "GIT",
"events": [
{
"introduced": "1abf272022cf1d18469405f47b4ec49c6a3125db"
},
{
"fixed": "57f94ac7e953eece5ed4819605a18f3cdfc63dcc"
},
{
"fixed": "942813276edeb1741fa5b0a73471beb4e495fa08"
},
{
"fixed": "cc707a4fd4c3b6ab2722e06bc359aa010e13d408"
},
{
"fixed": "4a09f72007201c9f667dc47f64517ec23eea65e5"
},
{
"fixed": "9bf5fc36a43f7b8b5507c96e74fb81f1e8b4957e"
},
{
"fixed": "a208c3e1232997e9317887294c20008dfcb75449"
},
{
"fixed": "415ea0c973c754b9f375225807810eb9045f4293"
},
{
"fixed": "1a280dd4bd1d616a01d6ffe0de284c907b555504"
}
]
}
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31422.json"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "4.15.0"
},
{
"fixed": "5.10.253"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "5.11.0"
},
{
"fixed": "5.15.203"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "5.16.0"
},
{
"fixed": "6.1.168"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.2.0"
},
{
"fixed": "6.6.134"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.7.0"
},
{
"fixed": "6.12.81"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.13.0"
},
{
"fixed": "6.18.22"
}
]
},
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "6.19.0"
},
{
"fixed": "6.19.12"
}
]
}
],
"package": {
"name": "Kernel",
"ecosystem": "Linux"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-31422.json"
}
}
],
"modified": "2026-10-28T02:30:28.057591428Z",
"provider": "osv",
"references": [
"https://cert-portal.siemens.com/productcert/html/ssa-019113.html",
"https://cert-portal.siemens.com/productcert/html/ssa-082556.html",
"https://cert-portal.siemens.com/productcert/html/ssa-457936.html",
"https://git.kernel.org/stable/c/1a280dd4bd1d616a01d6ffe0de284c907b555504",
"https://git.kernel.org/stable/c/415ea0c973c754b9f375225807810eb9045f4293",
"https://git.kernel.org/stable/c/4a09f72007201c9f667dc47f64517ec23eea65e5",
"https://git.kernel.org/stable/c/57f94ac7e953eece5ed4819605a18f3cdfc63dcc",
"https://git.kernel.org/stable/c/942813276edeb1741fa5b0a73471beb4e495fa08",
"https://git.kernel.org/stable/c/9bf5fc36a43f7b8b5507c96e74fb81f1e8b4957e",
"https://git.kernel.org/stable/c/a208c3e1232997e9317887294c20008dfcb75449",
"https://git.kernel.org/stable/c/cc707a4fd4c3b6ab2722e06bc359aa010e13d408",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31422.json",
"https://nvd.nist.gov/vuln/detail/CVE-2026-31422",
"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
],
"provider_metadata": {
"cna_assigner": "Linux",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31422.json"
}
},
"related_cves": [
{
"value": "CVE-2026-31422",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": null
},
"source_id": "core-osv",
"document_id": 494564,
"published_at": "2026-04-13T13:40:25.911+00:00"
}