Authenticated denial of service via unowned sessions
Published Jul 16, 2026 · Updated Jul 16, 2026
Denial of service in Microsoft UFO before 3.0.7 allows remote authenticated users to block tasks or exhaust server memory. The COMMAND_RESULTS WebSocket handler calls get_or_create_session without owner_client_id, creating attacker-chosen sessions with no recorded owner. A valid shared server token and a predictable session ID are required; a successful squat blocks the legitimate task, while repeated distinct IDs consume memory.
Summary
What happened
Denial of service in Microsoft UFO before 3.0.7 allows remote authenticated users to block tasks or exhaust server memory. The COMMAND_RESULTS WebSocket handler calls get_or_create_session without owner_client_id, creating attacker-chosen sessions with no recorded owner. A valid shared server token and a predictable session ID are required; a successful squat blocks the legitimate task, while repeated distinct IDs consume memory.
The record
- CVE
- CVE-2026-55440
- Published
- Jul 16, 2026
- Updated
- Jul 16, 2026
- Vendor
- Microsoft
- Product
- UFO
- Classifications
- CWE-862, CWE-400, T1499.004
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jul 16, 2026CVE publishedPublication date reported by the CVE source.
- Jul 16, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 3.0.7
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-hxjv-fmjf-wmjf proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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