THREATPORT/VULNERABILITY/CVE-2021-25830
CRITICAL SEVERITY

CVE-2021-25830

Document Server vulnerability

CVSS
9.8
EPSS
11.8%
EPSS pct
96th
Exploited
No known
A 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 of the crafted file from DOCT into DOCX format. Using the chain of two other bugs related to improper string handling, an attacker can achieve remote code execution on DocumentServer.
Affected vendor
Onlyoffice
Affected product
Document Server
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-03-01

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring no privileges, no user interaction. Successful exploitation leads to high impact to confidentiality, high impact to integrity, high impact to availability.

Its EPSS score of 11.8% reflects a moderate probability of exploitation activity in the wild over the next 30 days, placing it above 96% of all scored CVEs.

Check your external exposure to CVE-2021-25830

  • Confirm whether Onlyoffice Document Server is running on any internet-facing host or subdomain.
  • Match discovered service fingerprints against the version affected by CVE-2021-25830.
  • Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2021-25830

ThreatPort's external attack surface scanner checks your internet-facing assets — agentlessly, from the outside in — for the exposed services and versions that CVE-2021-25830 affects, then prioritises the finding by real risk using CISA KEV and FIRST.org EPSS.

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