CVE-2026-32241

Aliases:GHSA-vchx-5pr6-ffx2GO-2026-4894
Advisory lineage Upstream: 0 Downstream: 1
Analyzed
Published: 27 Mar 2026, 19:31
Last modified:31 Mar 2026, 18:54

Vulnerability Summary

Overall Risk (default)
medium
35/100
CVSS Score
8.8 HIGH
v3.1 (nvd)
EPSS Score
0.07% LOW
0% probability -0.17%
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

27 Mar 2026, 19:31
Published
Vulnerability first disclosed
31 Mar 2026, 18:54
Last Modified
Vulnerability information updated

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.

CVSS Metrics

  • v3.1•HIGH•Score: 7.5CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  • v3.1•HIGH•Score: 8.8CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Trends

Current EPSS score: 0.07%• Percentile: 21%

Techniques & Countermeasures

  • CWE-77•Improper Neutralization of Special Elements used in a Command ('Command Injection')

    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.

Affected Systems

  • flannel-io•flannel

    < 0.28.2

  • github.com/flannel-io•flannel

    < 0.28.2

References (5)