CVE-2021-25830Public exploitNetwork attack vector

Unauthenticated code execution via converter binary overwrite

Published Mar 1, 2021 · Updated Aug 3, 2024

File handling in ONLYOFFICE DocumentServer 4.2.0.236 through 5.6.4.13 allows remote attackers to execute code via DOCT-to-DOCX conversion. PPTX::Logic::UniFill::fromPPTY accepts an unvalidated inline-image extension, which GenerateImage uses to construct a filesystem path for an arbitrary overwrite. An unauthenticated conversion request can overwrite the x2t converter binary, while two string-handling faults force a crash before cleanup so the next request executes the replacement.

CVSS severity9.8
Critical
EPSS probability11.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

File handling in ONLYOFFICE DocumentServer 4.2.0.236 through 5.6.4.13 allows remote attackers to execute code via DOCT-to-DOCX conversion. PPTX::Logic::UniFill::fromPPTY accepts an unvalidated inline-image extension, which GenerateImage uses to construct a filesystem path for an arbitrary overwrite. An unauthenticated conversion request can overwrite the x2t converter binary, while two string-handling faults force a crash before cleanup so the next request executes the replacement.

The record

CVE
CVE-2021-25830
Published
Mar 1, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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