CVE-2020-11535

CVE-2020-11535 is a critical-severity vulnerability in Onlyoffice Document Server with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-91.

Key facts

• Severity: Critical (CVSS 3.x base score 9.8)
• CVSS v2: 7.5
• EPSS exploit prediction: 2% (81st percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-91
• Affected product: Onlyoffice Document Server
• Published: 2020-04-15
• Last modified: 2026-06-17

Description

An issue was discovered in ONLYOFFICE Document Server 5.5.0. An attacker can craft a malicious .docx file, and exploit XML injection to enter an attacker-controlled parameter into the x2t binary, to rewrite this binary and/or libxcb.so.1, and execute code on a victim's server.

Frequently asked questions

What is CVE-2020-11535?

An issue was discovered in ONLYOFFICE Document Server 5.5.0. An attacker can craft a malicious .docx file, and exploit XML injection to enter an attacker-controlled parameter into the x2t binary, to rewrite this binary and/or libxcb.so.1, and execute code on a victim's server.

How severe is CVE-2020-11535?

CVE-2020-11535 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-2020-11535 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-11535?

CVE-2020-11535 affects Onlyoffice Document Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-11535?

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-2020-11535 published?

CVE-2020-11535 was published on 2020-04-15 and last updated on 2026-06-17.

References

• https://gist.github.com/andrewaeva/beb92d3d2f1c5672dbda5050e323f6a0
• https://github.com/ONLYOFFICE/DocumentServer/blob/master/CHANGELOG.md#551

Affected products (1)

• cpe:2.3:a:onlyoffice:document_server:5.5.0:*:*:*:*:*:*:*

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Other CWE-91 (XML Injection) vulnerabilities

• CVE-2021-4140 — Critical (CVSS 10.0): It was possible to construct specific XSLT markup that would be able to bypass an iframe sandbox. This vulnerability…
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• CVE-2019-19450 — Critical (CVSS 9.8): paraparser in ReportLab before 3.5.31 allows remote code execution because start_unichar in paraparser.py evaluates…
• CVE-2021-37154 — Critical (CVSS 9.8): In ForgeRock Access Management (AM) before 7.0.2, the SAML2 implementation allows XML injection, potentially enabling a…
• CVE-2020-29128 — Critical (CVSS 9.8): petl before 1.68, in some configurations, allows resolution of entities in an XML document.
• CVE-2020-25216 — Critical (CVSS 9.8): yWorks yEd Desktop before 3.20.1 allows code execution via an XSL Transformation when using an XML file in conjunction…

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