# CVE-2026-32241: Flannel vulnerable to cross-node remote code execution via extension backend BackendData injection

> Attackers with node annotation access can execute arbitrary root commands on all cluster nodes via Flannel's experimental Extension backend.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:H/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Mar 2026
- **Updated:** 31 Mar 2026
- **Also known as:** AZL-80972, GHSA-vchx-5pr6-ffx2, GO-2026-4894, MINI-89rh-gh55-mj2v, MINI-rcj9-gfqc-xprg

## What is CVE-2026-32241?

CVE-2026-32241 is a high-severity command injection vulnerability in flannel-io flannel, published on 27 Mar 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Flannel is a network fabric for containers, designed for Kubernetes. The Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. In versions of Flannel prior to 0.28.2, this Extension backend is vulnerable to a command injection  that allows an attacker who can set Kubernetes Node annotations to achieve root-level arbitrary command execution on every flannel node in the cluster. The Extension backend's SubnetAddCommand and SubnetRemoveCommand receive attacker-controlled data via stdin (from the `flannel.alpha.coreos.com/backend-data` Node annotation). The content of this annotation is unmarshalled and piped directly to a shell command without checks. Kubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected. The vulnerability is fixed in version v0.28.2. As a workaround, use Flannel with another backend such as vxlan or wireguard.

Weakness: CWE-77 (Improper Neutralization of Special Elements used in a Command)

## Which versions are affected by CVE-2026-32241?

3 open source packages ship an affected version, including github.com/flannel-io/flannel. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/flannel-io/flannel` | Go | All versions | 0.28.2 |
| `github.com/flannel-io/flannel` | Go | All versions | 0.28.2 |
| `github.com/flannel-io/flannel` | Go | All versions | 0.28.2 |

Products: Flannel-Io Flannel.

## How do I fix CVE-2026-32241?

Upgrade github.com/flannel-io/flannel to 0.28.2 or later.

## Is CVE-2026-32241 being exploited?

There is no known exploitation of CVE-2026-32241 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-32241 and fix it if it is affected.

What it is: CVE-2026-32241 is a high-severity command injection vulnerability in flannel-io flannel, published on 27 Mar 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-2026-32241 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/flannel-io/flannel (Go): affected all versions; fixed in 0.28.2
- github.com/flannel-io/flannel (Go): affected all versions; fixed in 0.28.2
- github.com/flannel-io/flannel (Go): affected all versions; fixed in 0.28.2

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-2026-32241/ (Markdown: https://insights.sbomify.com/CVE-2026-32241/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-32241
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-32241
- OSV: https://osv.dev/vulnerability/CVE-2026-32241

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-32241/
Summaries are generated and may contain mistakes; the official description above is the record.