# CVE-2026-97598: ipv4: fib: bound automatic table ID allocation

> A local attacker can cause a denial of service in the Linux kernel by exhausting routing table IDs, leading to excessive CPU usage while holding the RTNL lock.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-104415, BELL-CVE-2026-97598, DEBIAN-CVE-2026-97598, GHSA-9pxv-wwmf-9jpr, UBUNTU-CVE-2026-97598

## What is CVE-2026-97598?

CVE-2026-97598 is a denial of service vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

ipv4: fib: bound automatic table ID allocation

fib_empty_table() probes every table ID from 1 until it finds a
free one.  IPv4 tables are stored in a 256-bucket hash table, so a
dense set of IDs makes each probe walk a growing hash chain while
RTNL is held.

Automatic table assignment ("ip rule ... table 0") is an IPv4-only
legacy path.  Bound the automatically allocated ID to 4096 so the
RTNL hold stays bounded, without changing lookups of explicitly
specified table IDs.

This changes user-visible behavior.  A table-0 rule previously
received the lowest free ID in 1..RT_TABLE_MAX (0xFFFFFFFF).  After
this patch the search stops at 4096 and the rule add fails with
ENOBUFS if that range is fully occupied.  Explicit table IDs above
4096 remain usable.

The automatic path is unused in practice: it is IPv4-only, not
documented by ip-rule, uncovered by kernel selftests, and both
NetworkManager and systemd refuse table 0.

## Which versions are affected by CVE-2026-97598?


## How do I fix CVE-2026-97598?

Apply the vendor's patch.

## Is CVE-2026-97598 being exploited?

There is no known exploitation of CVE-2026-97598 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97598 and fix it if it is affected.

What it is: CVE-2026-97598 is a denial of service vulnerability in Linux, published on 25 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-97598 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-2026-97598/ (Markdown: https://insights.sbomify.com/CVE-2026-97598/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97598
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97598
- OSV: https://osv.dev/vulnerability/CVE-2026-97598

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97598/
Summaries are generated and may contain mistakes; the official description above is the record.