CVE-2021-25829: ONLYOFFICE Document Server

High severity, CVSS 7.5. EPSS: 7.4% chance of exploitation in the next 30 days.

An improper binary stream data handling issue was found in the [core] module of ONLYOFFICE DocumentServer v4.0.0-9-v5.6.3. Using this bug, an attacker is able to produce a denial of service attack that can eventually shut down the target server.

Affected products

• ONLYOFFICE Document Server: from 4.0.0-9, up to and including 5.6.3

Published 2021-03-01. Last modified 2026-06-17.