CVE-2026-23636

Medium

Published: 25 March 2026

Published

25 March 2026

Modified

27 March 2026

KEV Added

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Patch

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CVSS Score 5.5 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:L

EPSS Score 0.0006 18.4th percentile

Risk Priority 11 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-23636 is a medium-severity Unrestricted Upload of File with Dangerous Type (CWE-434) vulnerability in Accellion Kiteworks. Its CVSS base score is 5.5 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 18.4th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

Directly addresses the missing validation allowing unrestricted upload of dangerous file types by enforcing comprehensive input validation on file uploads.

SI-9 Information Input Restrictions good match

prevent

Prevents exploitation by restricting the types and characteristics of uploaded files to exclude dangerous types.

SI-2 Flaw Remediation good match

prevent

Mitigates the vulnerability through timely flaw remediation, such as applying the patch to version 9.2.1 that adds the missing file upload validation.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1505.003 Web Shell Persistence

Adversaries may backdoor web servers with web shells to establish persistent access to systems.

attack.mitre.org →

Why these techniques?

Unrestricted file upload (CWE-434) in public-facing web app directly enables deployment of web shells or other malicious server components after authentication.

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

Kiteworks is a private data network (PDN). In Kiteworks Secure Data Forms prior to version 9.2.1, the manager of a form could potentially exploit an Unrestricted Upload of File with Dangerous Type due to a missing validation. Upgrade Kiteworks to…

version 9.2.1 or later to receive a patch.

Deeper analysisAI

CVE-2026-23636 is an Unrestricted Upload of File with Dangerous Type vulnerability (CWE-434) in Kiteworks Secure Data Forms prior to version 9.2.1. Kiteworks is a private data network (PDN), and the flaw arises from missing validation that allows managers of a form to upload dangerous file types.

The vulnerability requires high privileges (PR:H), specifically a form manager account, and can be exploited remotely over the network (AV:N) with low attack complexity (AC:L) and no user interaction (UI:N). Exploitation leads to high integrity impact (I:H) and low availability impact (A:L), with no confidentiality impact (C:N), yielding a CVSS v3.1 base score of 5.5 in an unchanged scope (S:U).

The Kiteworks security advisory recommends upgrading to version 9.2.1 or later to receive the patch that addresses the missing validation. Details are available in the GitHub Security Advisory at https://github.com/kiteworks/security-advisories/security/advisories/GHSA-cfv8-p3hq-8wmm.