VulnerabilityPublished 27 Mar 2026

CVE-2026-34391: fleetdm fleet · Exposure of Data Element to Wrong Session

Affects fleetdm fleetSource CVE Database V5

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Not known to be exploited · CVSS 6.6 Medium : upgrade to 4.81.1 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score

6.6Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.81.1

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:U

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: High
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: Unreported

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: Unreported: Based on threat intelligence sources each of the following must apply: · No knowledge of publicly available proof-of-concept · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 27 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 24 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade fleet and fleetdm/fleet to 4.81.1.

Affected software

Product	Affected	Fixed in
fleetdmfleet	Affected <4.81.1	Fixed in 4.81.1
GitHubfleetdm/fleet`pkg:github/fleetdm/fleet`Other threats	Affected <4.81.1	Fixed in 4.81.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Organizations should immediately upgrade Fleet to version 4.81.1 or later to apply the official patch that fixes the session isolation flaw. If you cannot patch yet, restrict enrollment of devices to trusted personnel only and monitor device enrollment logs for suspicious activity. Implement network segmentation to limit communication between managed devices and reduce the risk of lateral movement. Use endpoint detection and response (EDR) tools to detect anomalous behavior indicative of exploitation attempts. Regularly audit and rotate sensitive credentials such as WiFi and VPN secrets, and consider deploying certificate pinning or multi-factor authentication for critical services. Additionally, review Fleet’s configuration to ensure minimal privileges are granted to enrolled devices and enforce strict access controls. Conduct security awareness training to reduce the risk of malicious devices being introduced into the fleet. Finally, maintain up-to-date backups and incident response plans to quickly respond to any compromise.

Description

Fleet is open source device management software. Prior to 4.81.1, a vulnerability in Fleet's Windows MDM command processing allows a malicious enrolled device to access MDM commands intended for other devices, potentially exposing sensitive configuration data such as WiFi credentials, VPN secrets, and certificate payloads across the entire Windows fleet. Version 4.81.1 patches the issue.

Impact

The primary impact of CVE-2026-34391 is unauthorized disclosure of sensitive configuration data across an entire Windows device fleet managed by Fleet. Exposure of WiFi credentials and VPN secrets can enable attackers to gain unauthorized network access, potentially bypassing perimeter defenses. Certificate payload exposure may allow attackers to impersonate devices or users, undermining trust and enabling man-in-the-middle attacks. Since the vulnerability allows a malicious enrolled device to access data from other devices, it facilitates lateral movement within an organization’s network, increasing the risk of broader compromise. Organizations relying on Fleet for device management may face confidentiality breaches, regulatory compliance issues, and increased attack surface. The vulnerability’s exploitation does not require authentication or user interaction, making it easier for attackers to leverage once they have a foothold. Although no known exploits are reported, the potential for significant damage to enterprise security posture is substantial, especially in environments with many Windows endpoints managed via Fleet.

CWE-488Exposure of Data Element to Wrong Session (opens in a new tab)
Base weakness
The product does not sufficiently enforce boundaries between the states of different sessions, causing data to be provided to, or used by, the wrong session.
Architecture and Design
Protect the application's sessions from information leakage. Make sure that a session's data is not used or visible by other sessions.
Testing
Use a static analysis tool to scan the code for information leakage vulnerabilities (e.g. Singleton Member Field).
Architecture and Design
In a multithreading environment, storing user data in Servlet member fields introduces a data access race condition. Do not use member fields to store information in the Servlet.
Attack patterns
Session Credential Falsification through Prediction (opens in a new tab)
Reusing Session IDs (aka Session Replay) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/fleetdm/fleet/security/advisories/GHSA-wg7j-pcc3-h4rh (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 27 Mar 2026, 20:00 UTC

WeaknessesCWE-488

Technical details

References

Community reviews

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