# CVE-2026-72345: net/mlx5: LAG, Fix off-by-one in single-FDB error rollback

> An off-by-one error in the Linux kernel mlx5 LAG driver causes improper rollback of network rules, potentially leading to system instability or crashes.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-72345, DEBIAN-CVE-2026-72345, GHSA-2cj4-xv36-4974, UBUNTU-CVE-2026-72345

## What is CVE-2026-72345?

CVE-2026-72345 is a high-severity vulnerability in Linux, published on 15 Aug 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:

net/mlx5: LAG, Fix off-by-one in single-FDB error rollback

On failure at index i, the reverse cleanup loop in
mlx5_lag_create_single_fdb() starts from i, so the failed index
itself is rolled back. That can operate on uninitialized state or
double-tear-down a rule the add_one path already self-rolled-back.

Start the rollback from i - 1 so only successfully-installed entries
are undone.

## Which versions are affected by CVE-2026-72345?


## How do I fix CVE-2026-72345?

Apply the vendor's patch.

## Is CVE-2026-72345 being exploited?

There is no known exploitation of CVE-2026-72345 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72345 and fix it if it is affected.

What it is: CVE-2026-72345 is a high-severity vulnerability in Linux, published on 15 Aug 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-2026-72345 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-2026-72345/ (Markdown: https://insights.sbomify.com/CVE-2026-72345/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72345
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72345
- OSV: https://osv.dev/vulnerability/CVE-2026-72345

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72345/
Summaries are generated and may contain mistakes; the official description above is the record.