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netfilter: nft_flow_offload: drop flowtable reference on init error path

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_flow_offload: drop flowtable reference on init error path nft_flow_offload_init() bumps the flowtable use count with nft_use_inc() before calling nf_ct_netns_get(). When the latter fails, the error is returned as-is and the reference is leaked. The upper layers do not balance it either: nf_tables_newexpr() clears expr->ops when the expression init callback fails, so the nft_expr_more() iteration in nft_rule_expr_deactivate() and nf_tables_rule_destroy() stops right before the failed expression and its ->destroy callback, which would drop the reference, never runs. Each failed rule addition therefore leaks one flowtable reference and the flowtable can no longer be removed: NFT_MSG_DELFLOWTABLE keeps reporting -EBUSY even though no rule references it. Save the nf_ct_netns_get() return value and undo the nft_use_inc() when it fails, restoring the inc/dec pairing within nft_flow_offload_init() itself.

Products
Kernel
Affected versions
Not specified
Fixed versions
5.10.273, 5.15.224, 6.1.191, 6.12.113, 6.18.56, 6.6.160, 7.2.10
CVEs
CVE-2026-98851
Confirmed fixed CVEs
Not specified
Updated in this feed
3 Nov 2026, 07:45 UTC · Revision 1

Source evidence

netfilter: nft_flow_offload: drop flowtable reference on init error path

core-osv · Original source

Published 18 Oct 2026, 15:50 UTC

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_flow_offload: drop flowtable reference on init error path nft_flow_offload_init() bumps the flowtable use count with nft_use_inc() before calling nf_ct_netns_get(). When the latter fails, the error is returned as-is and the reference is leaked. The upper layers do not balance it either: nf_tables_newexpr() clears expr->ops when the expression init callback fails, so the nft_expr_more() iteration in nft_rule_expr_deactivate() and nf_tables_rule_destroy() stops right before the failed expression and its ->destroy callback, which would drop the reference, never runs. Each failed rule addition therefore leaks one flowtable reference and the flowtable can no longer be removed: NFT_MSG_DELFLOWTABLE keeps reporting -EBUSY even though no rule references it. Save the nf_ct_netns_get() return value and undo the nft_use_inc() when it fails, restoring the inc/dec pairing within nft_flow_offload_init() itself.

osv:CVE-2026-98851

Kernel

Fixed versions: 5.10.273, 5.15.224, 6.1.191, 6.6.160, 6.12.113, 6.18.56, 7.2.10

Complete source record
{
  "id": "7581e0b79f8b7e10e5144fa58bdd80b1c569c25fc507efccbf47d5f9882dd7ba",
  "url": "https://osv.dev/vulnerability/CVE-2026-98851",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "netfilter: nft_flow_offload: drop flowtable reference on init error path",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_flow_offload: drop flowtable reference on init error path nft_flow_offload_init() bumps the flowtable use count with nft_use_inc() before calling nf_ct_netns_get(). When the latter fails, the error is returned as-is and the reference is leaked. The upper layers do not balance it either: nf_tables_newexpr() clears expr->ops when the expression init callback fails, so the nft_expr_more() iteration in nft_rule_expr_deactivate() and nf_tables_rule_destroy() stops right before the failed expression and its ->destroy callback, which would drop the reference, never runs. Each failed rule addition therefore leaks one flowtable reference and the flowtable can no longer be removed: NFT_MSG_DELFLOWTABLE keeps reporting -EBUSY even though no rule references it. Save the nf_ct_netns_get() return value and undo the nft_use_inc() when it fails, restoring the inc/dec pairing within nft_flow_offload_init() itself.",
    "evidence": "osv:CVE-2026-98851",
    "products": [
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        "affected_versions": []
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    "severity": "unknown",
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      "aliases": [
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      "modified": "2026-11-01T02:30:28.159843852Z",
      "provider": "osv",
      "references": [
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        "https://git.kernel.org/stable/c/1f43b6b099fa39032780b9494cedfd98f318f3c4",
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        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98851.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98851",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
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      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98851.json"
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    "related_cves": [
      {
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    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 493496,
  "published_at": "2026-10-18T15:50:50.91+00:00"
}