# CVE-2025-71097: ipv4: Fix reference count leak when using error routes with nexthop objects

> A reference count leak in the Linux kernel IPv4 routing code can prevent network device removal, leading to resource exhaustion and denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **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:** 13 Jan 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2025-71097, DEBIAN-CVE-2025-71097, GHSA-hc39-xg82-jgf4, ROOT-OS-DEBIAN-11-CVE-2025-71097, ROOT-OS-DEBIAN-12-CVE-2025-71097, ROOT-OS-DEBIAN-13-CVE-2025-71097, ROOT-OS-UBUNTU-2204-CVE-2025-71097, ROOT-OS-UBUNTU-2404-CVE-2025-71097, UBUNTU-CVE-2025-71097

## What is CVE-2025-71097?

CVE-2025-71097 is a medium-severity denial of service vulnerability in Linux kernel, published on 13 Jan 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: Fix reference count leak when using error routes with nexthop objects

When a nexthop object is deleted, it is marked as dead and then
fib_table_flush() is called to flush all the routes that are using the
dead nexthop.

The current logic in fib_table_flush() is to only flush error routes
(e.g., blackhole) when it is called as part of network namespace
dismantle (i.e., with flush_all=true). Therefore, error routes are not
flushed when their nexthop object is deleted:

 # ip link add name dummy1 up type dummy
 # ip nexthop add id 1 dev dummy1
 # ip route add 198.51.100.1/32 nhid 1
 # ip route add blackhole 198.51.100.2/32 nhid 1
 # ip nexthop del id 1
 # ip route show
 blackhole 198.51.100.2 nhid 1 dev dummy1

As such, they keep holding a reference on the nexthop object which in
turn holds a reference on the nexthop device, resulting in a reference
count leak:

 # ip link del dev dummy1
 [   70.516258] unregister_netdevice: waiting for dummy1 to become free. Usage count = 2

Fix by flushing error routes when their nexthop is marked as dead.

IPv6 does not suffer from this problem.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2025-71097?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-71097?

Apply the vendor's patch.

## Is CVE-2025-71097 being exploited?

There is no known exploitation of CVE-2025-71097 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-71097 and fix it if it is affected.

What it is: CVE-2025-71097 is a medium-severity denial of service vulnerability in Linux kernel, published on 13 Jan 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-2025-71097 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2025-71097/ (Markdown: https://insights.sbomify.com/CVE-2025-71097/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-71097
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-71097
- OSV: https://osv.dev/vulnerability/CVE-2025-71097

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-71097/
Summaries are generated and may contain mistakes; the official description above is the record.