CVE-2021-25831

CriticalCVSS 9.8/10Last modified Jun 17, 2026

Description

A file extension handling issue was found in [core] module of ONLYOFFICE DocumentServer v4.0.0-9-v5.6.3. An attacker must request the conversion of the crafted file from PPTT into PPTX format. Using the chain of two other bugs related to improper string handling, a remote attacker can obtain remote code execution on DocumentServer.

Metrics

CVSS 3.1 9.8/10CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected software

Vendor	Product	Versions
n/a	n/a	n/a

References

https://github.com/ONLYOFFICE/DocumentServerProduct
https://github.com/ONLYOFFICE/coreProduct, Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/Fills/BlipFill.cpp#L328Vendor Advisory
https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831Exploit, Vendor Advisory
https://github.com/ONLYOFFICE/DocumentServerProduct
https://github.com/ONLYOFFICE/coreProduct, Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/Fills/BlipFill.cpp#L328Vendor Advisory
https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831Exploit, Vendor Advisory

Timeline

Published: Mar 1, 2021
Last modified: Jun 17, 2026
NVD status: Modified

Related CVEs from 2021

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