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    CVE-2021-25831

    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.

    Published:Mar 1, 2021
    Last Modified:Nov 21, 2024
    EPS:Mar 1, 2021
    EPSS Score:0.03615
    CVSS Score:9.8

    Affected Products

    Vendor
    Onlyoffice
    Product
    Document Server

    Exploits

    https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831

    Common Weakness Enumeration

    No CWE recorded yet

    Common Attack Pattern Enumeration and Classification (CAPEC)

    No CAPEC recorded yet

    Related CVEs

    CVE-2026-41034 (CVSS 5) — ONLYOFFICE DocumentServer before 9.3.0 has an untrusted pointer dereference in XLS processing/conversion (via …
    CVE-2025-68936 (CVSS 6.4) — ONLYOFFICE Docs before 9.2.1 allows XSS via the Color theme name. This is related to DocumentServer.…
    CVE-2025-68935 (CVSS 6.4) — ONLYOFFICE Docs before 9.2.1 allows XSS via the Font field for the Multilevel list settings window. This is re…
    CVE-2025-68917 (CVSS 6.4) — ONLYOFFICE Docs before 9.2.1 allows XSS in the textarea of the comment editing form. This is related to Docume…
    CVE-2023-46988 (CVSS 6.7) — Path Traversal vulnerability in ONLYOFFICE Document Server before v8.0.1 allows a remote attacker to copy arbi…
    CVE-2023-50883 (CVSS 6.1) — ONLYOFFICE Docs before 8.0.1 allows XSS because a macro is an immediately-invoked function expression (IIFE), …
    CVE-2023-30188 (CVSS 7.5) — Memory Exhaustion vulnerability in ONLYOFFICE Document Server 4.0.3 through 7.3.2 allows remote attackers to c…
    CVE-2023-30186 (CVSS 9.8) — A use after free issue discovered in ONLYOFFICE DocumentServer 4.0.3 through 7.3.2 allows remote attackers to …
    CVE-2023-30187 (CVSS 9.8) — An out of bounds memory access vulnerability in ONLYOFFICE DocumentServer 4.0.3 through 7.3.2 allows remote at…
    CVE-2022-48422 (CVSS 7.8) — ONLYOFFICE Docs through 7.3 on certain Linux distributions allows local users to gain privileges via a Trojan …

    References

    https://github.com/ONLYOFFICE/DocumentServer
    https://github.com/ONLYOFFICE/core
    https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918
    https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241
    https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/Fills/BlipFill.cpp#L328
    https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831
    https://github.com/ONLYOFFICE/DocumentServer
    https://github.com/ONLYOFFICE/core
    https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L1918
    https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/Editor/BinaryFileReaderWriter.cpp#L241
    https://github.com/ONLYOFFICE/core/blob/v5.6.4.13/ASCOfficePPTXFile/PPTXFormat/Logic/Fills/BlipFill.cpp#L328
    https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25831

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High