CVE-2026-32241: Github.com/flannel io/flannel Remote Code Execution Vulnerability
HIGHCVE-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.
CVE-2026-32241 at a Glance
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).
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.
Upgrade github.com/flannel-io/flannel to 0.28.2Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for github.com/flannel-io/flannelHow 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/flannelAnalyze 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
CVE-2026-32241 Affected Github.com/flannel io/flannel Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/flannel-io/flannel
|
Go |
< 0.28.2
|
0.28.2
|
References
Frequently Asked Questions
What is CVE-2026-32241?
Which Github.com/flannel io/flannel versions are affected?
What version fixes CVE-2026-32241?
Is github.com/flannel-io/flannel affected?
What is the CVSS score of CVE-2026-32241?
What CWE is associated with CVE-2026-32241?
How can I check Go dependencies for CVE-2026-32241?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"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"
}
}