Raw vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-32241 is a high-severity Command Injection (CWE-77) vulnerability in Flannel-Io Flannel. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Command and Scripting Interpreter (T1059); ranked in the top 15% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-32241 is a command injection vulnerability in the experimental Extension backend of Flannel, an overlay network fabric designed for Kubernetes container orchestration. Affecting Flannel versions prior to 0.28.2, the flaw occurs because the Extension backend's SubnetAddCommand and SubnetRemoveCommand processes attacker-controlled data from the Kubernetes Node annotation `flannel.alpha.coreos.com/backend-data`. This data is unmarshalled and piped directly to a shell command without validation, enabling injection. Only the Extension backend is impacted; other backends like vxlan and wireguard remain unaffected.
An attacker with low privileges who can set Kubernetes Node annotations (consistent with the CVSS v3.1 base score of 7.5: AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H) can exploit this to achieve root-level arbitrary command execution on every Flannel node in the cluster. The attack requires network access and high complexity, such as crafting malicious annotation data that exploits the stdin-fed shell invocation (CWE-77: Command Injection).
The Flannel security advisory (GHSA-vchx-5pr6-ffx2) and release notes for v0.28.2 confirm the issue is fixed in that version. As a workaround, administrators should switch to a different backend such as vxlan or wireguard to avoid using the vulnerable Extension backend entirely.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-16771
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can discover command-construction flaws before deployment.
Input validation directly stops construction of commands from untrusted data containing special elements.
Secure engineering principles include proper neutralization and safe command construction practices.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Runtime monitoring of software and data can detect anomalous command execution resulting from injection.
Identifying recorded vulnerabilities enables remediation of command-injection flaws before exploitation.
Secure SDLC practices directly require input validation and neutralization that prevent command injection.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Secure development life cycle mandates input validation and command construction practices that directly prevent command injection.
Application security requirements explicitly call for controls against injection flaws including command injection.
Secure architecture principles reduce the attack surface but do not prescribe the specific neutralization techniques needed.
Secure coding standards require proper escaping and parameterization of commands, directly eliminating CWE-77.
Security testing in development catches command-injection vulnerabilities before release.