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Vulnerability record · CVE-2021-25833 · published 1 March 2021

CVE-2021-25833: Onlyoffice document server path traversal vulnerability

Onlyoffice · Document Server

A 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 attacker through the request data and leads to arbitrary file overwriting. Using this vulnerability, a remote attacker can obtain remote code execution on DocumentServer.

9.8 CVSS 3.1 Critical EPSS 44% · top 1.3% CWE-22 · Path traversal
9.8CVSS 3.1 base score, v2 7.5
44%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
12References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

A 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 attacker through the request data and leads to arbitrary file overwriting. Using this vulnerability, a remote attacker can obtain remote code execution on DocumentServer.

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

Affected products

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

References

LinkTags
https://github.com/ONLYOFFICE/DocumentServer ProductVendor Advisory
https://github.com/ONLYOFFICE/server Product
https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/DocService/sources/converterservice.js#L200 Third Party Advisory
https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/FileConverter/sources/converter.js#L283 Third Party Advisory
https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/FileConverter/sources/converter.js#L593 Third Party Advisory
https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25833 ExploitThird Party Advisory
https://github.com/ONLYOFFICE/DocumentServer ProductVendor Advisory
https://github.com/ONLYOFFICE/server Product
https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/DocService/sources/converterservice.js#L200 Third Party Advisory
https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/FileConverter/sources/converter.js#L283 Third Party Advisory
https://github.com/ONLYOFFICE/server/blob/v5.6.0.21/FileConverter/sources/converter.js#L593 Third Party Advisory
https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25833 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-2021-3199Onlyoffice document server path traversal vulnerabilityDirectory traversal with remote code execution can occur in /upload in ONLYOFFICE Document Server before 5.6.3, when JWT is used, via a /.. sequence …EPSS 8.2%

Source: NIST National Vulnerability Database (record CVE-2021-25833), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.