---
id: "CVE-2026-98586"
kind: "vulnerability"
aliases: ["CVE-2026-98586"]
title: "Linux kernel SCTP: timer race can free objects and underflow refcounts"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["linux-kernel", "runtime", "sctp"]
not_affected_if: []
published_at: "2026-10-18T16:17:11+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:22:56+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98586", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel SCTP: timer race can free objects and underflow refcounts

A race in the Linux kernel's SCTP timer handlers can rearm a timer on an association or transport after cleanup has already dropped its reference. The timer then takes a reference on freed memory, causing a refcount underflow.

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

## How to check

- unknown

## Fix

- unknown

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98586

## From the sources

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

sctp: hold asoc or transport before mod_timer() in timer handlers

Take the association or transport reference before rearming a timer in the
timer handlers.

The existing code calls mod_timer() before taking the reference needed by
the rearmed timer without holding the sock lock. This creates a race with
timer cleanup: if the timer is deleted after mod_timer() returns but before
the reference is taken, the cleanup path can drop the timer's reference and
destroy the transport or association. The timer handler then takes a
reference on the already freed object and eventually drops it, causing a
refcount underflow.

Hold the object before mod_timer() and drop the reference if mod_timer()
reports that the timer was already pending in timer handlers. Apply the
same ordering to the proto-unreachable path, which can rearm a transport
timer outside the timer handlers without holding the sock lock.

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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_