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CVE-2021-25830

35
FAUCET Score

CVE-2021-25830 is a critical remote code execution (RCE) vulnerability affecting ONLYOFFICE DocumentServer versions 4.2.0.236 through 5.6.4.13. This flaw stems from a file extension handling issue within the core module, which, when combined with two other string handling bugs, allows an unauthenticated attacker to execute arbitrary code by requesting the conversion of a specially crafted DOCT file to DOCX format. With a CVSS score of 9.8, this vulnerability presents a severe risk due to its network-based attack vector, low complexity, and complete compromise of confidentiality, integrity, and availability. Despite its critical severity, there is currently no public exploit code available (Metasploit, Nuclei, ExploitDB), nor is there evidence of active exploitation or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
>= 4.2.0.236, <= 5.6.4.13CPE matchmatch criteria
cpe:2.3:a:onlyoffice:document_server:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
11.76%
Probability of exploitation in next 30 days
EPSS Percentile
95.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.1176 is in the 91st percentile among its peer group of 36,835 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

github.com / merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830
ExploitThird Party Advisory
github.com / ONLYOFFICE/core
Product
github.com / ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp
Third Party Advisory
github.com / ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp
Third Party Advisory
github.com / ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/UniFill.cpp
Third Party Advisory
github.com / ONLYOFFICE/DocumentServer
Product