Vulnerabilities in pkg:golang/github.com/flannel-io/flannel

PACKAGE
Advisory Identifier: GHSA-vchx-5pr6-ffx2
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Advisory Summary

CVE-2026-32241 is a HIGH (CVSS 7.5) remote code execution vulnerability (CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')) affecting Github.com/flannel io/flannel libraries in the Go ecosystem. The issue involves flannel has cross-node remote code execution via extension backend backenddata injection. Remediation is available by upgrading affected packages to version 0.28.2.

1 Known Advisory Record(s)
Package Vulnerability Intelligence

pkg:golang/github.com/flannel-io/flannel

1 Known Advisory Record(s)

Vulnerability advisories affecting package pkg:golang/github.com/flannel-io/flannel. Select an advisory below to view technical details or fixes.

Advisory ID CVE / NVD Severity Summary
GHSA-vchx-5pr6-ffx2 CVE-2026-32241 HIGH Flannel has cross-node remote code execution via extension backend BackendData injection

CVE-2026-32241 at a Glance

CVE Identifier CVE-2026-32241
GHSA Identifier GHSA-vchx-5pr6-ffx2
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
Affected Product Github.com/flannel io/flannel
Package Ecosystem Go
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-32241

To remediate this vulnerability, upgrade all affected Github.com/flannel io/flannel dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

github.com/flannel-io/flannel fixed: 0.28.2 
Upgrade github.com/flannel-io/flannel to 0.28.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for github.com/flannel-io/flannel

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-32241, inspect your project dependencies for Github.com/flannel io/flannel:

inspect dependencies for github.com/flannel-io/flannel

Analyze the terminal output to locate any version of Github.com/flannel io/flannel in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.28.2), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection'), where the product constructs all or part of an os command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended os command when it is sent to a downstream component. In Github.com/flannel io/flannel, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Background The Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. This backend uses shell commands stored in Kubernetes annotations to configure network connectivity on the node. Note: consumers are only affected by this vulnerability if they use the experimental Extension backend. Other backends such as vxlan and wireguard are unaffected. ### Vulnerability 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. ### Impact Kubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected. ### Patches This is fixed in version v0.28.2. ### Workaround If consumers cannot update to a patched version, then use Flannel with another backend such as vxlan or wireguard. ### Credits Flannel would like to thank Shachar Tal from Palo Alto Networks for reporting this vulnerability.

CVE-2026-32241 Affected Github.com/flannel io/flannel Versions

1 component(s)
Fixed Versions:
0.28.2
Product / Package Ecosystem Affected Versions Fixed Version
github.com/flannel-io/flannel
golang/github.com/flannel-io/flannel
Go
< 0.28.2
0.28.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/flannel-io/flannel/security/advisories/GHSA-vchx-5pr6-ffx2
NVD — CVE-2026-32241 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-32241
Security Fix Commit FIX COMMIT
https://github.com/flannel-io/flannel/commit/08bc9a4c990ae785d2fcb448f4991b58485cd26a
Github.com/flannel io/flannel Source Repository REPOSITORY
https://github.com/flannel-io/flannel
Github.com/flannel io/flannel Release RELEASE
https://github.com/flannel-io/flannel/releases/tag/v0.28.2

Frequently Asked Questions

What is CVE-2026-32241?
CVE-2026-32241 is a security vulnerability in Github.com/flannel io/flannel involving Flannel has cross-node remote code execution via extension backend BackendData injection under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection').
Which Github.com/flannel io/flannel versions are affected?
Affected versions include releases prior to 0.28.2 across affected packages: github.com/flannel-io/flannel.
What version fixes CVE-2026-32241?
Upgrading to 0.28.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/flannel-io/flannel affected?
Yes, github.com/flannel-io/flannel is affected in releases prior to 0.28.2. Upgrade your dependency to 0.28.2 or later.
What is the CVSS score of CVE-2026-32241?
CVE-2026-32241 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-32241?
CVE-2026-32241 is classified under CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') (The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.).
How can I check Go dependencies for CVE-2026-32241?
Run the dependency tree command: 'inspect dependencies for github.com/flannel-io/flannel'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-vchx-5pr6-ffx2",
  "modified" : "2026-03-27T21:48:12Z",
  "published" : "2026-03-27T20:28:13Z",
  "aliases" : [ "CVE-2026-32241" ],
  "summary" : "Flannel has cross-node remote code execution via extension backend BackendData injection",
  "details" : "### Background\nThe Flannel project includes an experimental Extension backend that allows users to easily prototype new backend types. This backend uses shell commands stored in Kubernetes annotations to configure network connectivity on the node.\n\nNote: consumers are only affected by this vulnerability if they use the experimental Extension backend. Other backends such as vxlan and wireguard are unaffected.\n\n### Vulnerability\nThis 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.\n\nThe 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.\n\n### Impact\nKubernetes clusters using Flannel with the Extension backend are affected by this vulnerability. Other backends such as vxlan and wireguard are unaffected.\n\n### Patches\nThis is fixed in version v0.28.2.\n\n### Workaround \nIf consumers cannot update to a patched version, then use Flannel with another backend such as vxlan or wireguard.\n\n### Credits\nFlannel would like to thank  Shachar Tal from Palo Alto Networks for reporting this vulnerability.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/flannel-io/flannel"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.28.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.28.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/flannel-io/flannel/security/advisories/GHSA-vchx-5pr6-ffx2"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-32241"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/flannel-io/flannel/commit/08bc9a4c990ae785d2fcb448f4991b58485cd26a"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/flannel-io/flannel"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/flannel-io/flannel/releases/tag/v0.28.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-77", "CWE-78" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-27T20:28:13Z",
    "nvd_published_at" : "2026-03-27T20:16:30Z"
  }
}