# CVE-2026-98586: sctp: hold asoc or transport before mod_timer() in timer handlers

> A race condition in Linux kernel SCTP timer handlers allows use-after-free, potentially leading to denial of service or code execution.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-108647, BELL-CVE-2026-98586, DEBIAN-CVE-2026-98586, GHSA-4473-fgjm-w85x, UBUNTU-CVE-2026-98586

## What is CVE-2026-98586?

CVE-2026-98586 is an use after free vulnerability in Linux, published on 18 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

## Which versions are affected by CVE-2026-98586?


## How do I fix CVE-2026-98586?

Apply the vendor's patch.

## Is CVE-2026-98586 being exploited?

There is no known exploitation of CVE-2026-98586 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98586 and fix it if it is affected.

What it is: CVE-2026-98586 is an use after free vulnerability in Linux, published on 18 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98586 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98586/ (Markdown: https://insights.sbomify.com/CVE-2026-98586/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98586
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98586
- OSV: https://osv.dev/vulnerability/CVE-2026-98586

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98586/
Summaries are generated and may contain mistakes; the official description above is the record.