Critical severity9.8NVD Advisory· Published Mar 1, 2021· Updated Jun 17, 2026
CVE-2021-25830
CVE-2021-25830
Description
A file extension handling issue was found in [core] module of ONLYOFFICE DocumentServer v4.2.0.236-v5.6.4.13. An attacker must request the conversion of the crafted file from DOCT into DOCX format. Using the chain of two other bugs related to improper string handling, an attacker can achieve remote code execution on DocumentServer.
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Affected products
3- cpe:2.3:a:onlyoffice:document_server:*:*:*:*:*:*:*:*Range: >=4.2.0.236,<=5.6.4.13
- ONLYOFFICE/DocumentServerdescription
- Range: v4.2.0.236-v5.6.4.13
Patches
Vulnerability mechanics
References
4- github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830nvdExploitThird Party Advisory
- github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cppnvdThird Party Advisory
- github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cppnvdThird Party Advisory
- github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/UniFill.cppnvdThird Party Advisory
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