CVE-2021-25832

CVE-2021-25832 is a critical-severity vulnerability in Onlyoffice Document Server with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 13% places it in the 96th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-787.

Key facts

• Severity: Critical (CVSS 3.x base score 9.8)
• CVSS v2: 7.5
• EPSS exploit prediction: 13% (96th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-787
• Affected product: Onlyoffice Document Server
• Published: 2021-03-01
• Last modified: 2026-06-17

Description

A heap buffer overflow vulnerability inside of BMP image processing was found at [core] module of ONLYOFFICE DocumentServer v4.0.0-9-v6.0.0. Using this vulnerability, an attacker is able to gain remote code executions on DocumentServer.

Frequently asked questions

What is CVE-2021-25832?

A heap buffer overflow vulnerability inside of BMP image processing was found at [core] module of ONLYOFFICE DocumentServer v4.0.0-9-v6.0.0. Using this vulnerability, an attacker is able to gain remote code executions on DocumentServer.

How severe is CVE-2021-25832?

CVE-2021-25832 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-25832 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 13% (96th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-25832?

CVE-2021-25832 affects Onlyoffice Document Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-25832?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-25832 published?

CVE-2021-25832 was published on 2021-03-01 and last updated on 2026-06-17.

References

• https://github.com/ONLYOFFICE/DocumentServer
• https://github.com/ONLYOFFICE/core
• https://github.com/ONLYOFFICE/core/blob/v6.0.1.15/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L424
• https://github.com/ONLYOFFICE/core/blob/v6.0.1.15/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L428
• https://github.com/ONLYOFFICE/core/blob/v6.0.1.15/DesktopEditor/cximage/CxImage/ximabmp.cpp#L354
• https://github.com/ONLYOFFICE/core/blob/v6.0.1.15/DesktopEditor/cximage/CxImage/ximabmp.cpp#L358
• https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25832

Affected products (1)

• cpe:2.3:a:onlyoffice:document_server:*:*:*:*:*:*:*:*

More vulnerabilities in Onlyoffice Document Server

• CVE-2023-30187 — Critical (CVSS 9.8): An out of bounds memory access vulnerability in ONLYOFFICE DocumentServer 4.0.3 through 7.3.2 allows remote attackers…
• CVE-2023-30186 — Critical (CVSS 9.8): A use after free issue discovered in ONLYOFFICE DocumentServer 4.0.3 through 7.3.2 allows remote attackers to run…
• CVE-2022-29777 — Critical (CVSS 9.8): Onlyoffice Document Server v6.0.0 and below and Core 6.1.0.26 and below were discovered to contain a heap overflow via…
• CVE-2022-29776 — Critical (CVSS 9.8): Onlyoffice Document Server v6.0.0 and below and Core 6.1.0.26 and below were discovered to contain a stack overflow via…
• CVE-2021-25833 — Critical (CVSS 9.8): A file extension handling issue was found in [server] module of ONLYOFFICE DocumentServer v4.2.0.71-v5.6.0.21. The file…
• CVE-2021-25831 — Critical (CVSS 9.8): A file extension handling issue was found in [core] module of ONLYOFFICE DocumentServer v4.0.0-9-v5.6.3. An attacker…

All CVEs affecting Onlyoffice Document Server →

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