# CVE-2026-98596: ipv6: Fix dst leak for uncached routes.

> A race condition in the Linux kernel IPv6 routing code can lead to a destination cache leak, potentially causing memory exhaustion and denial of service.

- **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:** BELL-CVE-2026-98596, DEBIAN-CVE-2026-98596, GHSA-gvvq-54cj-7xg4, UBUNTU-CVE-2026-98596

## What is CVE-2026-98596?

CVE-2026-98596 is a 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:

ipv6: Fix dst leak for uncached routes.

ip6_route_output_flags(), ip6_rt_put_flags(), and ip6_dst_check()
detect an uncached route by list_empty(&rt->dst.rt_uncached),
which replaced the static DST_NOCACHE flag check in commit
a4c2fd7f7891 ("net: remove DST_NOCACHE flag").

When a device is unregistered, rt6_uncached_list_flush_dev()
unlinks uncached routes tied to the device from rt6_uncached_list.

Previously, they were moved to another list with list_move()
(__list_del_entry() + list_add()), and since commit 98aa546af5e4
("inet: remove (struct uncached_list)->quarantine"), the routes
are just unlinked with list_del_init().

If list_del_init() runs concurrently, list_empty() evaluates to
true; ip6_route_output_flags() calls dst_hold_safe() incorrectly
and ip6_rt_put_flags() skips ip6_rt_put(), leaking dst, and thus
dev tied via rt->from as well.

The same race is partially fixed by commit 9a6f0c4d5796 ("dst:
fix races in rt6_uncached_list_del() and rt_del_uncached_list()").

Let's check rt6->dst.rt_uncached_list instead.

Note that IPv4 does not have the same issue.

## Which versions are affected by CVE-2026-98596?


## How do I fix CVE-2026-98596?

Apply the vendor's patch.

## Is CVE-2026-98596 being exploited?

There is no known exploitation of CVE-2026-98596 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98596 and fix it if it is affected.

What it is: CVE-2026-98596 is a 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-2026-98596 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-2026-98596/ (Markdown: https://insights.sbomify.com/CVE-2026-98596/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98596
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98596
- OSV: https://osv.dev/vulnerability/CVE-2026-98596

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98596/
Summaries are generated and may contain mistakes; the official description above is the record.