---
id: "CVE-2026-98851"
kind: "vulnerability"
aliases: ["CVE-2026-98851"]
title: "Linux kernel: failed nftables flow offload rule leaks flowtable reference"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["kernel", "linux", "nftables", "runtime", "self-hosted"]
not_affected_if: ["no-nftables-flowtables"]
published_at: "2026-10-18T16:17:39+00:00"
first_seen_at: "2026-10-23T21:57:17+00:00"
updated_at: "2026-10-25T05:13:02+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98851", "first_seen_at": "2026-10-23T21:57:17+00:00"}]
---

# Linux kernel: failed nftables flow offload rule leaks flowtable reference

When adding an nftables flow offload rule fails, the kernel leaks a flowtable reference on each failed attempt. The leaked reference stops the flowtable from being deleted, so NFT_MSG_DELFLOWTABLE keeps returning -EBUSY.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-23T21:57:17+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98851

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_