Modbus service interruption via unreleased socket descriptors
Published Oct 7, 2025 · Updated Oct 7, 2025
Denial of service in OpenPLC Runtime v3 a931181e8b81e36fadf7b74d5cba99b73c3f6d58 allows remote attackers to interrupt ModbusTCP processing. The startServer path assigns each connection to a blocking handleConnections thread, while readModbusMessage waits indefinitely without releasing abandoned socket descriptors. Unauthenticated network access to TCP port 502 is sufficient; exhausting descriptors and holding a final connection open prevents subsequent Modbus requests.
Summary
What happened
Denial of service in OpenPLC Runtime v3 a931181e8b81e36fadf7b74d5cba99b73c3f6d58 allows remote attackers to interrupt ModbusTCP processing. The startServer path assigns each connection to a blocking handleConnections thread, while readModbusMessage waits indefinitely without releasing abandoned socket descriptors. Unauthenticated network access to TCP port 502 is sufficient; exhausting descriptors and holding a final connection open prevents subsequent Modbus requests.
The record
- CVE
- CVE-2025-53476
- Published
- Oct 7, 2025
- Updated
- Oct 7, 2025
- Vendor
- OpenPLC Project
- Product
- OpenPLC Runtime v3
- Classifications
- CWE-775, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Oct 7, 2025CVE publishedPublication date reported by the CVE source.
- Oct 7, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=a931181e8b81e36fadf7b74d5cba99b73c3f6d58
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
- Cisco Talos ModbusTCP descriptor-exhaustion demonstrationproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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