CVE-2026-1331

Critical

Published: 22 January 2026

Published

22 January 2026

Modified

17 February 2026

KEV Added

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Patch

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CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0009 25.7th percentile

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

Summary

CVE-2026-1331 is a critical-severity Unrestricted Upload of File with Dangerous Type (CWE-434) vulnerability in Hamastar Meetinghub Paperless Meetings. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 25.7th 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-2 Flaw Remediation good match

prevent

Directly remediates the arbitrary file upload vulnerability in MeetingHub by applying vendor patches or updates as referenced in TWCERT advisories.

SI-10 Information Input Validation good match

prevent

Validates file upload inputs to block arbitrary web shell uploads and prevent remote code execution.

SI-3 Malicious Code Protection good match

preventdetect

Scans and eradicates malicious web shells uploaded via the vulnerable unauthenticated endpoint.

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?

Arbitrary file upload on public-facing web app directly enables initial access via exploitation (T1190) and web shell deployment for code execution (T1505.003).

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

NVD Description

MeetingHub developed by HAMASTAR Technology has an Arbitrary File Upload vulnerability, allowing unauthenticated remote attackers to upload and execute web shell backdoors, thereby enabling arbitrary code execution on the server.

Deeper analysisAI

CVE-2026-1331 is an Arbitrary File Upload vulnerability (CWE-434) affecting MeetingHub, a product developed by HAMASTAR Technology. Published on 2026-01-22, the flaw has a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), marking it as critical. It enables unauthenticated remote attackers to upload web shell backdoors and execute arbitrary code on the server.

Unauthenticated remote attackers can exploit this vulnerability over the network with low attack complexity, no required privileges, and no user interaction. Exploitation allows attackers to upload and execute malicious web shells, achieving arbitrary code execution on the server and resulting in high impacts to confidentiality, integrity, and availability.

Advisories from TWCERT provide details on this vulnerability, available at https://www.twcert.org.tw/en/cp-139-10651-ff09c-2.html and https://www.twcert.org.tw/tw/cp-132-10650-a5ee9-1.html. Security practitioners should review these references for recommended mitigations and patches.