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Vulnerability record · CVE-2021-25829 · published 1 March 2021

CVE-2021-25829: Onlyoffice document server vulnerability

Onlyoffice · Document Server

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.

7.5 CVSS 3.1 High EPSS 7.4% · top 5.8%
7.5CVSS 3.1 base score, v2 7.8
7.4%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
20References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/ONLYOFFICE/DocumentServer Product
https://github.com/ONLYOFFICE/core ProductVendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/Comments.h Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/Core.h#L16 Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/NotesMaste Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/NotesSlide Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/Presentati Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/Theme.h#L2 Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/v5.6.4.10/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1722 Vendor Advisory
https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25829 ExploitThird Party Advisory
https://github.com/ONLYOFFICE/DocumentServer Product
https://github.com/ONLYOFFICE/core ProductVendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/Comments.h Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/Core.h#L16 Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/NotesMaste Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/NotesSlide Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/Presentati Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/c1e4a2ce33bdcfab29d670f5fdb10fc63cf5fd6a/ASCOfficePPTXFile/PPTXFormat/Theme.h#L2 Vendor Advisory
https://github.com/ONLYOFFICE/core/blob/v5.6.4.10/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1722 Vendor Advisory
https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25829 ExploitThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2023-30186Onlyoffice document server use after free vulnerabilityA use after free issue discovered in ONLYOFFICE DocumentServer 4.0.3 through 7.3.2 allows remote attackers to run arbitrary code via crafted JavaScri…EPSS 2.3%9.8CVE-2023-30187Onlyoffice document server out-of-bounds write vulnerabilityAn out of bounds memory access vulnerability in ONLYOFFICE DocumentServer 4.0.3 through 7.3.2 allows remote attackers to run arbitrary code via craft…EPSS 2.4%9.8CVE-2022-29776Onlyoffice core out-of-bounds write vulnerabilityOnlyoffice Document Server v6.0.0 and below and Core 6.1.0.26 and below were discovered to contain a stack overflow via the component DesktopEditor/c…EPSS 6.9%9.8CVE-2022-29777Onlyoffice core out-of-bounds write vulnerabilityOnlyoffice Document Server v6.0.0 and below and Core 6.1.0.26 and below were discovered to contain a heap overflow via the component DesktopEditor/fo…EPSS 6.9%9.8CVE-2021-25830Onlyoffice document server vulnerabilityA 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…EPSS 12%9.8CVE-2021-25831Onlyoffice document server vulnerabilityA 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 t…EPSS 12%9.8CVE-2021-25832Onlyoffice document server out-of-bounds write vulnerabilityA heap buffer overflow vulnerability inside of BMP image processing was found at [core] module of ONLYOFFICE DocumentServer v4.0.0-9-v6.0.0. Using th…EPSS 13%9.8CVE-2021-25833Onlyoffice document server path traversal vulnerabilityA file extension handling issue was found in [server] module of ONLYOFFICE DocumentServer v4.2.0.71-v5.6.0.21. The file extension is controlled by an…EPSS 44%

Source: NIST National Vulnerability Database (record CVE-2021-25829), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.