# CVE-2026-97597: ipv6: flowlabel: cap duplicate leases per socket

> An unprivileged local user can exhaust kernel memory by repeatedly requesting IPv6 flow labels, causing a denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-104370, BELL-CVE-2026-97597, DEBIAN-CVE-2026-97597, GHSA-7x5f-23mf-qfp3, UBUNTU-CVE-2026-97597

## What is CVE-2026-97597?

CVE-2026-97597 is a denial of service vulnerability in Linux, published on 25 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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

ipv6: flowlabel: cap duplicate leases per socket

ipv6_flowlabel_get() allocates an ipv6_fl_socklist entry for every
successful GET. The recheck path for a compatible existing flowlabel
links another lease without applying any lease admission check. Repeated
GET requests for one shareable label can therefore grow a socket's lease
list without bound.

Reject a new unprivileged lease once the socket already holds
FL_MAX_PER_SOCK leases. Check this on the shared recheck path so reuse
of a globally interned label, including the fl_intern() collision path,
is covered as well. New-label admission remains under the existing
mem_check() policy.

Use capable(CAP_NET_ADMIN) rather than ns_capable(), matching
mem_check(). An unprivileged user must not bypass the cap by creating a
user namespace and a netns where they have CAP_NET_ADMIN, which would
still consume host memory.

Check the capability only when the socket reaches the limit, so
successful unprivileged GET requests below the cap do not generate a
capability audit. Do the admission check before updating linger and
expires so a rejected GET does not refresh the shared label, matching
the existing socket-list allocation failure path.

## Which versions are affected by CVE-2026-97597?


## How do I fix CVE-2026-97597?

Apply the vendor's patch.

## Is CVE-2026-97597 being exploited?

There is no known exploitation of CVE-2026-97597 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97597 and fix it if it is affected.

What it is: CVE-2026-97597 is a denial of service vulnerability in Linux, published on 25 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-97597 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-2026-97597/ (Markdown: https://insights.sbomify.com/CVE-2026-97597/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97597
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97597
- OSV: https://osv.dev/vulnerability/CVE-2026-97597

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97597/
Summaries are generated and may contain mistakes; the official description above is the record.