---
id: "CVE-2026-98625"
kind: "vulnerability"
aliases: ["CVE-2026-98625"]
title: "Linux kernel: flowtable offload worker can cause use-after-free"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["linux-kernel", "netfilter", "nftables", "runtime", "self-hosted"]
not_affected_if: ["no-flowtable-configured"]
published_at: "2026-10-18T16:17:15+00:00"
first_seen_at: "2026-10-23T21:57:16+00:00"
updated_at: "2026-10-25T05:21:11+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98625", "first_seen_at": "2026-10-23T21:57:16+00:00"}]
---

# Linux kernel: flowtable offload worker can cause use-after-free

In the Linux netfilter flowtable code, a flow can be marked dead before the offload worker finishes with it, so garbage collection may free it while the worker still uses it. The sources describe this as a use-after-free, which can lead to a crash or memory corruption in the kernel.

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

## How to check

- `uname -r` to see the running kernel version
- Check whether the flowtable feature is in use: `nft list ruleset | grep -i flowtable`
- unknown for the exact vulnerable version range

## Fix

- Update the Linux kernel to a release that includes the upstream netfilter flowtable fix (version unknown from sources)
- Reboot after installing the patched kernel

## Timeline

- 2026-10-23T21:57:16+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98625

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

netfilter: flowtable: publish HW_DEAD after worker is done

flow_offload_work_del() sets NF_FLOW_HW_DEAD before the work handler
clears NF_FLOW_HW_PENDING. Once a flow is both HW_DYING and HW_DEAD, a
concurrent garbage collection pass can remove it and schedule it for RCU
freeing.

The offload worker holds neither an RCU read lock nor a reference to the
flow. If it is preempted after publishing HW_DEAD, the RCU callback can
free the flow before the worker resumes and clears HW_PENDING, resulting
in a use-after-free.

Move HW_DEAD publication to the common worker epilogue after the pending
bit is cleared, making it the final flow access by destroy work. Order all
preceding flow accesses before publishing the bit that allows garbage
collection to free the object.

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