CVE-2026-78587 PUBLISHED

Incorrect Authorization in Fleet Server Leading to Denial of Service of Agent Upload Operations

Assigner: elastic
Reserved: 24.08.2026 Published: 02.09.2026 Updated: 02.09.2026

Incorrect Authorization (CWE-863) in Fleet Server can lead to a denial of service of agent upload operations via Privilege Abuse (CAPEC-122). Fleet Server does not correctly verify session ownership during multi-part data upload operations, allowing any authenticated agent to interfere with the active upload sessions belonging to other enrolled agents.

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L
CVSS Score: 3.1

Attack Vector	Network	Scope	Unchanged
Attack Complexity	High	Confidentiality Impact	None
Privileges Required	Low	Integrity Impact	None
User Interaction	None	Availability Impact	Low

CVSS 3.1

Product Status

Vendor	Elastic
Product	Fleet Server
Versions	Default: unaffected affected from 8.0.0 to 8.19.15 (incl.) affected from 9.0.0 to 9.3.4 (incl.) affected from 9.4.0 to 9.4.1 (incl.)

References

https://discuss.elastic.co/t/fleet-server-8-19-16-9-3-5-9-4-2-security-update-esa-2026-164/390117

Problem Types

CWE-863 Incorrect Authorization CWE

Impacts

CAPEC-122 Privilege Abuse