# CVE-2026-34388: Fleet vulnerable to Denial of Service via unhandled gRPC log type in launcher endpoint

> An authenticated host can crash the Fleet server by sending an unexpected log type, disrupting all connected devices and services.

- **Severity:** Medium 6.6 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Mar 2026
- **Updated:** 31 Mar 2026
- **Also known as:** GHSA-w254-4hp5-7cvv, GO-2026-4915

## What is CVE-2026-34388?

CVE-2026-34388 is a medium-severity denial of service vulnerability in fleetdm fleet, published on 27 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Fleet is open source device management software. Prior to 4.81.0, a denial-of-service vulnerability in Fleet's gRPC Launcher endpoint allows an authenticated host to crash the entire Fleet server process by sending an unexpected log type value. The server terminates immediately, disrupting all connected hosts, MDM enrollments, and API consumers. Version 4.81.0 patches the issue.

Weakness: CWE-703 (Improper Check or Handling of Exceptional Conditions)

## Which versions are affected by CVE-2026-34388?

3 open source packages ship an affected version, including github.com/fleetdm/fleet/v4. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/fleetdm/fleet/v4` | Go | All versions | 4.81.0 |
| `github.com/fleetdm/fleet/v4` | Go | All versions | 4.81.0 |
| `github.com/fleetdm/fleet/v4` | Go | All versions | 4.81.0 |

Products: Fleetdm Fleet.

## How do I fix CVE-2026-34388?

Upgrade github.com/fleetdm/fleet/v4 to 4.81.0 or later.

## Is CVE-2026-34388 being exploited?

There is no known exploitation of CVE-2026-34388 in the wild and no public exploit code.

## Other vulnerabilities in fleetdm fleet

- [CVE-2020-26276](https://insights.sbomify.com/CVE-2020-26276/): SAML authentication vulnerability in Fleet (critical 10.0)
- [CVE-2026-103264](https://insights.sbomify.com/CVE-2026-103264/): Fleet before 4.87.0 Authentication Bypass via Device Identifiers (critical 9.3)
- [CVE-2026-23518](https://insights.sbomify.com/CVE-2026-23518/): Fleet has a JWT signature bypass vulnerability in Azure AD MDM enrollment (critical 9.3)
- [CVE-2026-26062](https://insights.sbomify.com/CVE-2026-26062/): Fleet server may terminate unexpectedly when handling certain gRPC requests (high 8.7)
- [CVE-2026-26061](https://insights.sbomify.com/CVE-2026-26061/): Fleet's unbounded request body read allows remote Denial of Service (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34388 and fix it if it is affected.

What it is: CVE-2026-34388 is a medium-severity denial of service vulnerability in fleetdm fleet, published on 27 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-34388 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/fleetdm/fleet/v4 (Go): affected all versions; fixed in 4.81.0
- github.com/fleetdm/fleet/v4 (Go): affected all versions; fixed in 4.81.0
- github.com/fleetdm/fleet/v4 (Go): affected all versions; fixed in 4.81.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-34388/ (Markdown: https://insights.sbomify.com/CVE-2026-34388/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34388
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34388
- OSV: https://osv.dev/vulnerability/CVE-2026-34388

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34388/
Summaries are generated and may contain mistakes; the official description above is the record.