GHSA-j8h8-75h3-jg53
MEDIUMGHSA-j8h8-75h3-jg53 is a medium-severity (CVSS 5.3) CWE-290 vulnerability in github.com/fleetdm/fleet/v4. O3 Security confirms whether GHSA-j8h8-75h3-jg53 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Fleet has a rate limiting bypass via untrusted client IP headers
EPSS Exploitation Probability
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.
How urgent is this, really
GHSA-j8h8-75h3-jg53 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 357,322 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
github.com/fleetdm/fleet/v4Real-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
Impact
Fleet trusted client-supplied IP address headers when determining the source IP for incoming requests. This allowed authenticated and unauthenticated clients to spoof their apparent IP address and bypass per-IP rate limiting controls.
Fleet determines a client’s public IP address using HTTP headers such as:
- X-Forwarded-For
- X-Real-IP
- True-Client-IP
These headers were trusted without validation. An attacker could supply arbitrary values in these headers, causing Fleet to treat each request as originating from a different IP address.
This could allow an attacker to bypass per-IP rate limits and increase the effectiveness of brute-force or password-spraying attempts against authentication endpoints.
This issue does not allow authentication bypass, privilege escalation, data exposure, or remote code execution on its own.
Workarounds
Run Fleet behind a trusted reverse proxy or load balancer that overwrites client IP headers.
For more information
If you have any questions or comments about this advisory:
Email us at [email protected] Join #fleet in osquery Slack
Credits
We thank @fuzzztf for responsibly reporting this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/fleetdm/fleet/v4 | all versions | 4.80.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/fleetdm/fleet/v4. 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/fleetdm/fleet/v4 to 4.80.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-j8h8-75h3-jg53 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-j8h8-75h3-jg53 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-j8h8-75h3-jg53. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-j8h8-75h3-jg53 in your dependencies?
O3 detects GHSA-j8h8-75h3-jg53 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.