How severe is GHSA-9vcr-g537-3w5v?

No CVSS score has been assigned to GHSA-9vcr-g537-3w5v yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-9vcr-g537-3w5v?

GHSA-9vcr-g537-3w5v affects the following packages: github.com/fleetdm/fleet/v4 (Go). Ecosystems affected: Go.

How do I fix GHSA-9vcr-g537-3w5v?

Update github.com/fleetdm/fleet/v4 to 4.81.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9vcr-g537-3w5v is resolved across your whole dependency graph.

How do I detect GHSA-9vcr-g537-3w5v in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/fleetdm/fleet/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-9vcr-g537-3w5v if there is no patch (or I can't update yet)?

Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Is GHSA-9vcr-g537-3w5v actively exploited in the wild?

No public exploit code has been indexed for GHSA-9vcr-g537-3w5v 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-9vcr-g537-3w5v?

GHSA-9vcr-g537-3w5v has an EPSS (Exploit Prediction Scoring System) score of 0.9%, placing it in the 59th 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-9vcr-g537-3w5v?

GHSA-9vcr-g537-3w5v is classified as OS Command Injection (CWE-78). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was GHSA-9vcr-g537-3w5v published, and has it been updated?

GHSA-9vcr-g537-3w5v was published on May 14, 2026 and was last updated on June 25, 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

Not in CISA KEV

GHSA-9vcr-g537-3w5v — v4

GHSA-9vcr-g537-3w5v is a OS Command Injection vulnerability in github.com/fleetdm/fleet/v4. A fix is available for github.com/fleetdm/fleet/v4 — see the affected versions and patch details below.

Fleet vulnerable to OS command injection in software packages

Also known asCVE-2026-26191GO-2026-5301

Published

May 14, 2026

Updated

Jun 25, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 27, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-9vcr-g537-3w5v.

EPSS Exploitation Probability

via FIRST.org ↗

0.9%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs59th percentile — riskier than 59% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐹github.com/fleetdm/fleet/v4

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

Summary

A vulnerability in Fleet's software installer pipeline could allow a crafted software package to execute arbitrary commands as root (macOS/Linux) or SYSTEM (Windows) on managed endpoints when an uninstall is triggered.

Impact

When a software package (.pkg, .deb, .rpm, .exe, or .msi) is uploaded to Fleet, metadata is extracted from the package binary and used to generate uninstall scripts. In affected versions, this metadata is not properly sanitized before being included in the generated scripts. A specially crafted package containing malicious values in its metadata fields could result in unintended command execution when the uninstall script runs on managed endpoints.

Workarounds

If an immediate upgrade is not possible, administrators should avoid uploading software packages obtained from untrusted or unverified sources. Additionally, administrators can manually inspect and edit auto-generated uninstall scripts before deployment.

For more information

If you have any questions or comments about this advisory:

Email us at [[email protected]](mailto:[email protected])

Join #fleet in [osquery Slack](https://join.slack.com/t/osquery/shared_invite/zt-h29zm0gk-s2DBtGUTW4CFel0f0IjTEw)

Credits

We thank @secfox-ai for responsibly reporting this issue.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/fleetdm/fleet/v4`	all versions	4.81.1`go get github.com/fleetdm/fleet/v4@v4.81.1`

Affected Products

1 product · 1 configurations

Application

fleetfleetdm

< 4.81.0

range

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/fleetdm/fleet/v4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/fleetdm/fleet/v4 to 4.81.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9vcr-g537-3w5v is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Frequently Asked Questions

### Summary A vulnerability in Fleet's software installer pipeline could allow a crafted software package to execute arbitrary commands as root (macOS/Linux) or SYSTEM (Windows) on managed endpoints when an uninstall is triggered. ### Impact When a software package (.pkg, .deb, .rpm, .exe, or .msi) is uploaded to Fleet, metadata is extracted from the package binary and used to generate uninstall scripts. In affected versions, this metadata is not properly sanitized before being included in the generated scripts. A specially crafted package containing malicious values in its metadata fields

O3 Security · Impact-Aware SCA

Is GHSA-9vcr-g537-3w5v in your dependencies?

Find it across Go, including transitive dependencies.

Scan my dependencies How O3 SCA works

GHSA-9vcr-g537-3w5v — v4

Exploitation Status

No confirmed exploitation observed yet

EPSS Exploitation Probability

Real-World Exposure

Description

Summary

Impact

Workarounds

For more information

Credits

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is GHSA-9vcr-g537-3w5v in your dependencies?