CVE-2021-28799 is an improper authorization vulnerability in QNAP Hybrid Backup Sync 3 (HBS 3) that allows remote attackers to log in to affected NAS devices. Exploitation uses a hard-coded session identifier to bypass authentication and execute commands, enabling malware deployment. Affected HBS 3 releases are versions before 16.0.0415 on QTS 4.5.2, before 3.0.210412 on QTS 4.3.6, before 3.0.210411 on QTS 4.3.4 and 4.3.3, and before 16.0.0419 on QuTS hero h4.5.1 and QuTScloud c4.5.1 through c4.5.4. HBS 2 and HBS 1.3 are unaffected.
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What an attacker gets, and what they’ve been doing with it.
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Patch, then assume compromise.
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No public exploit code observed for this vulnerability.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
13 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A CVE record whose template CVSS score metadata was being corrected to agree with its CVSS metrics vector and NVD's computed score.
An improper authorization vulnerability in QNAP HBS 3 (Hybrid Backup Sync) allows remote attackers to log in to affected NAS devices.
A remote code execution vulnerability affecting QNAP NAS devices, mentioned as a possible initial access vector used to compromise the FTP server that hosted SockDetour.
A remote code execution vulnerability referenced as the likely flaw used to compromise a QNAP NAS delivery server previously infected with QLocker ransomware.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.