HOMEVULNERABILITIESCVE-2021-25831
CRITICAL

CVE-2021-25831

NVD-CWE-noinfoPublished: March 1, 2021· Updated: Jun 17, 2026

9.8
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-25831 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected Vendors & Products

onlyoffice1 product(s)
document server
Source: NVD CPE · 1 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://github.com/ONLYOFFICE/core
ADVISORYhttps://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918
ADVISORYhttps://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241
ADVISORYhttps://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/Fills/BlipFill.cpp#L328
ADVISORYhttps://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831
ADVISORYhttps://github.com/ONLYOFFICE/core
ADVISORYhttps://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918
ADVISORYhttps://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241
ADVISORYhttps://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/Fills/BlipFill.cpp#L328
ADVISORYhttps://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831

All References (12)

→
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

Quick Facts

CVE IDCVE-2021-25831
CVSS Score9.8 / 10
SeverityCRITICAL
WeaknessNVD-CWE-noinfo
CISA KEVNo
Affected1 vendor(s)
PublishedMar 1, 2021

Related CVEs (NVD-CWE-noinfo)

CVE-2014-1548
10.0
CVE-2014-3525
10.0
CVE-2014-4227
10.0
CVE-2014-1547
10.0
CVE-2014-0609
10.0
CVE-2014-2632
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-25831 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
← All Vulnerabilities·Search for CVE-2021-25831·NVD