Cyber Resilience

CVE-2026-34388

Fleetdm Fleet ≤ 4.81.0

Published
27 March 2026
Modified
02 April 2026
Patch / advisory
View advisory
CVSS Score v4 6.6
Click a component to see what it means
Raw vectorCVSS: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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0026 18th percentile
Risk Priority 39 floored blend · peak EPSS

Summary

CVE-2026-34388 is a medium-severity Improper Check or Handling of Exceptional Conditions (CWE-703) vulnerability in Fleetdm Fleet. Its CVSS base score is 6.6 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 18th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SC-24 (Fail in Known State) and SI-17 (Fail-safe Procedures) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-34388 is a denial-of-service vulnerability in Fleet, an open source device management software. The issue affects versions prior to 4.81.0 and resides in Fleet's gRPC Launcher endpoint, where the server fails to handle an unexpected log type value properly, leading to an immediate process termination. This flaw is classified under CWE-703 (Improper Check or Handling of Exceptional Conditions) and carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), highlighting its high availability impact with network accessibility and low complexity.

An authenticated host enrolled in Fleet can exploit this vulnerability by sending a specially crafted unexpected log type value via the gRPC Launcher endpoint. Successful exploitation crashes the entire Fleet server process without warning, resulting in widespread disruption: all connected hosts lose management capabilities, MDM enrollments fail, and API consumers are blocked from operations until the server restarts. Attackers require only valid host authentication, typically granted during normal device enrollment.

The Fleet security advisory at https://github.com/fleetdm/fleet/security/advisories/GHSA-w254-4hp5-7cvv details the patch in version 4.81.0, which addresses the improper handling in the gRPC endpoint. Security practitioners should upgrade to 4.81.0 or later and monitor for anomalous gRPC traffic from enrolled hosts to mitigate exposure.

OWASP Top 10 for Web (2025)

A10:2025 Mishandling of Exceptional Conditions

EU & UK References

Vulnerability Data

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,…

more

disrupting all connected hosts, MDM enrollments, and API consumers. Version 4.81.0 patches the issue.

CWE(s)
CWE-703

Related Threats

MITRE ATT&CK Enterprise Techniques

T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
attack.mitre.org →
T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-26062Same product: Fleetdm Fleet
CVE-2026-29180Same product: Fleetdm Fleet
CVE-2026-23517Same product: Fleetdm Fleet
CVE-2026-24004Same product: Fleetdm Fleet
CVE-2026-25963Same product: Fleetdm Fleet
CVE-2026-34386Same product: Fleetdm Fleet
CVE-2026-26186Same product: Fleetdm Fleet
CVE-2026-34385Same product: Fleetdm Fleet
CVE-2026-34387Same product: Fleetdm Fleet
CVE-2026-22808Same product: Fleetdm Fleet

Affected Assets

fleetdm
fleet
≤ 4.81.0

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SC-24 Fail in Known State good match

Enforces failure to a known state while preserving required properties, limiting impact of unhandled exceptions.

SI-17 Fail-safe Procedures good match

Mandates explicit fail-safe procedures triggered by indicated failures, structurally preventing unhandled exceptional conditions.

SA-8 Security and Privacy Engineering Principles partial match

Requires application of security engineering principles that include robust exception and error handling during design.

SI-11 Error Handling partial match

Requires generation of safe, actionable error messages that directly addresses proper handling of exceptional conditions.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices explicitly require anticipating and correctly handling exceptional conditions during design and coding.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.6.8 Information security event reporting none match
none

Reporting of unhandled errors or exceptional conditions surfaces latent failure paths so they can be corrected before exploitation.

References