Summaryinfo

A vulnerability marked as critical has been reported in flannel-io flannel up to 0.28.1. This affects an unknown part. Performing a manipulation results in command injection. This vulnerability is known as CVE-2026-32241. Remote exploitation of the attack is possible. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in flannel-io flannel up to 0.28.1. This affects an unknown code. The manipulation with an unknown input leads to a command injection vulnerability. CWE is classifying the issue as CWE-77. The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-32241 since 03/11/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1202 according to MITRE ATT&CK.

Upgrading to version 0.28.2 eliminates this vulnerability. The upgrade is hosted for download at github.com.

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Productinfo

Vendor

• flannel-io

Name

• flannel

Version

• 0.28.0
• 0.28.1

Website

• Product: https://github.com/flannel-io/flannel/

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