AUGUST 4, 2026
Live Feed
Back to database
Case File

CVE-2021-28799

CRITICAL · CVSS 10 EPSS 78.25% CISA KEV · Actively Exploited Public Exploit

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2021-05-13 · Last synced 2026-08-04

CyberRota Analysis

AI analysis pending.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Detected Signals
exploit

Note: these links are listed for security research and verification purposes only.

CISA KEV Details

Status: This CVE is listed in CISA's Known Exploited Vulnerabilities catalog.

Ransomware use: Known

Added to KEV: 2022-03-31

Required action: Apply updates per vendor instructions.

CVE
CVE-2021-28799
Severity
CRITICAL
CVSS
10
EPSS
78.25%

Original NVD Description

An improper authorization vulnerability has been reported to affect QNAP NAS running HBS 3 (Hybrid Backup Sync. ) If exploited, the vulnerability allows remote attackers to log in to a device. This issue affects: QNAP Systems Inc. HBS 3 versions prior to v16.0.0415 on QTS 4.5.2; versions prior to v3.0.210412 on QTS 4.3.6; versions prior to v3.0.210411 on QTS 4.3.4; versions prior to v3.0.210411 on QTS 4.3.3; versions prior to v16.0.0419 on QuTS hero h4.5.1; versions prior to v16.0.0419 on QuTScloud c4.5.1~c4.5.4. This issue does not affect: QNAP Systems Inc. HBS 2 . QNAP Systems Inc. HBS 1.3 .