CRITICAL

CVE-2021-25831

CVSS v3

9.8

CRITICAL

EPSS Score

11.5 %

exploit probability, as of 2026-10-18

CISA KEV

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2021-25831 yet.

Full record on NVD

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.

Technical details

Published: 2021-03-01

Frequently asked questions

What is CVE-2021-25831?

Is CVE-2021-25831 actively exploited?

Active exploitation of CVE-2021-25831 has not been confirmed. Its EPSS score was 11.5% on 2026-10-18, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-25831?

CVE-2021-25831 has a CVSS v3 base score of 9.8 (CRITICAL severity).

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