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.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
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 | 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 include Flannel-Io Flannel.
How do I fix CVE-2026-32241?
Upgrade github.com/flannel-io/flannel to 0.28.2 or later.
Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.
Is CVE-2026-32241 being exploited?
There is no known exploitation of CVE-2026-32241 in the wild and no public exploit code.
Sources
Also known as AZL-80972, GHSA-vchx-5pr6-ffx2, GO-2026-4894, MINI-89rh-gh55-mj2v, MINI-rcj9-gfqc-xprg.