How severe is GHSA-vchx-5pr6-ffx2?

GHSA-vchx-5pr6-ffx2 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-vchx-5pr6-ffx2?

GHSA-vchx-5pr6-ffx2 affects the following packages: github.com/flannel-io/flannel (Go). Ecosystems affected: Go.

How do I fix GHSA-vchx-5pr6-ffx2?

Update github.com/flannel-io/flannel to 0.28.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vchx-5pr6-ffx2 is resolved across your whole dependency graph.

How do I detect GHSA-vchx-5pr6-ffx2 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/flannel-io/flannel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-vchx-5pr6-ffx2 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-vchx-5pr6-ffx2?

O3 pinpoints whether GHSA-vchx-5pr6-ffx2 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-vchx-5pr6-ffx2 actively exploited in the wild?

No public exploit code has been indexed for GHSA-vchx-5pr6-ffx2 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-vchx-5pr6-ffx2?

GHSA-vchx-5pr6-ffx2 has an EPSS (Exploit Prediction Scoring System) score of 2.7%, placing it in the 84th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-vchx-5pr6-ffx2?

GHSA-vchx-5pr6-ffx2 is classified as CWE-77 (CWE-77). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-vchx-5pr6-ffx2 published, and has it been updated?

GHSA-vchx-5pr6-ffx2 was published on March 27, 2026 and was last updated on April 2, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

GHSA-vchx-5pr6-ffx2

HIGH

Flannel has cross-node remote code execution via extension backend BackendData injection

Also known asCVE-2026-32241GO-2026-4894

Published

Mar 27, 2026

Updated

Apr 2, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

2.7%probability of exploitation in next 30 days

Lower Risk84th percentile+2.64%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

🐹github.com/flannel-io/flannel

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/flannel-io/flannel`	all versions	0.28.2

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/flannel-io/flannel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/flannel-io/flannel to 0.28.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vchx-5pr6-ffx2 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-vchx-5pr6-ffx2 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-vchx-5pr6-ffx2. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### 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 execu

O3 Security · Impact-Aware SCA

Is GHSA-vchx-5pr6-ffx2 in your dependencies?

O3 detects GHSA-vchx-5pr6-ffx2 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works