Topic disclosure via truncated UTF-8 length
Published Dec 2, 2025 · Updated Dec 2, 2025
Numeric truncation in Eclipse Paho MQTT Go client 1.5.0 and earlier allows remote attackers to disclose topic data via oversized strings. The MQTT encoder narrows an unchecked string length from an int to an int16, writes the truncated length, and then emits the complete byte sequence. Exposure requires an application to pass an attacker-influenced UTF-8 field longer than 65,535 bytes, allowing excess topic bytes to enter the PUBLISH body.
Summary
What happened
Numeric truncation in Eclipse Paho MQTT Go client 1.5.0 and earlier allows remote attackers to disclose topic data via oversized strings. The MQTT encoder narrows an unchecked string length from an int to an int16, writes the truncated length, and then emits the complete byte sequence. Exposure requires an application to pass an attacker-influenced UTF-8 field longer than 65,535 bytes, allowing excess topic bytes to enter the PUBLISH body.
The record
- CVE
- CVE-2025-10543
- Published
- Dec 2, 2025
- Updated
- Dec 2, 2025
- Vendor
- The Eclipse Foundation
- Product
- Eclipse Paho MQTT Go client
- Classifications
- CWE-681, CWE-197, T1565.002
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Dec 2, 2025CVE publishedPublication date reported by the CVE source.
- Dec 2, 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=0 <=1.5.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
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Weakness, pattern, technique
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Technologies
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Your stack
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