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CVE-2020-9054

Zyxel — Zyxel Multiple NAS Devices OS Command Injection Vulnerability

Zyxel · CWE-78 — Operating system command injection · in CISA KEV since 2022-03-25

ExigentKEV since 2022 · listed over a yearCISA KEVActively Exploited
87

EVRS 87 of 100 Immediate

Out-of-Band / Urgent Remediation

Rank 209 of 2,960 tracked

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Why it scores 87

Evidence available: 6 of 7 signals

Listed in the CISA KEV catalog, and an EPSS probability of 0.999.

  • CISA KEVApplied
  • RansomwareDid not apply
  • Vendor exploitationDid not apply
  • EPSSApplied
  • Microsoft Exploitability IndexNot applicable
  • Pre-patch disclosureNo data
  • KEV recencyDid not apply
  • CVSSApplied

The band answers “how soon”, not “how bad”. No data for: Pre-patch disclosure. Why some signals show no data

Fix

Patch or fixed version identified

CISA required action

Fixed in

nas326 firmware: update to 5.21\(aazf.10\)c0 or later | nas520 firmware: update to 5.21\(aasz.3\)c0 or later | nas540 firmware: update to 5.21\(aatb.7\)c0 or later | nas542 firmware: update to 5.21\(abag.7\)c0 or later | atp100 firmware: update to 4.35\(abps.3\)c0 or later | atp200 firmware: update to 4.35\(abfw.3\)c0 or later

Affected versions

  • nas326 firmware< 5.21\(aazf.10\)c0
  • nas520 firmware< 5.21\(aasz.3\)c0
  • nas540 firmware< 5.21\(aatb.7\)c0
  • nas542 firmware< 5.21\(abag.7\)c0
  • atp100 firmware>= 4.35 < 4.35\(abps.3\)c0
  • atp200 firmware>= 4.35 < 4.35\(abfw.3\)c0
  • atp500 firmware>= 4.35 < 4.35\(abfu.3\)c0
  • atp800 firmware>= 4.35 < 4.35\(abiq.3\)c0

+46 more affected products; see the full list at NVD.

Remediation

Apply updates per vendor instructions.

Fixed versions from NVD.

Evidence

Each value with its source
MeasureValueSource
CVSS base scoreHow severe the flaw is in itself. It does not say how likely an attack is. 9.8 NVD
FIRST EPSSFIRST's estimate of the chance this is exploited in the next 30 days, and how that ranks against all CVEs. 0.999 (99.98th pctl) FIRST EPSS
Actively exploitedWhether a source of record has confirmed attacks using it in the wild. Confirmed CISA KEV
Ransomware campaign useWhether CISA has seen ransomware operators use it. Unknown or none CISA KEV
CISA remediation deadlineThe date US federal agencies must have fixed or mitigated it. 2022-04-15 · KEV since 2022 · listed over a year CISA KEV
Public exploit moduleA module existing is not the same as active exploitation. None known Metasploit
EUVD cross-referenceENISA's record: CVSS 9.8 (v3.1), assigned by certcc. Listed ENISA EUVD

Description

NVD

Multiple ZyXEL network-attached storage (NAS) devices running firmware version 5.21 contain a pre-authentication command injection vulnerability, which may allow a remote, unauthenticated attacker to execute arbitrary code on a vulnerable device. ZyXEL NAS devices achieve authentication by using the weblogin.cgi CGI executable. This program fails to properly sanitize the username parameter that is passed to it. If the username parameter contains certain characters, it can allow command injection with the privileges of the web server that runs on the ZyXEL device. Although the web server does not run as the root user, ZyXEL devices include a setuid utility that can be leveraged to run any command with root privileges. As such, it should be assumed that exploitation of this vulnerability can lead to remote code execution with root privileges. By sending a specially-crafted HTTP POST or GET request to a vulnerable ZyXEL device, a remote, unauthenticated attacker may be able to execute arbitrary code on the device. This may happen by directly connecting to a device if it is directly exposed to an attacker. However, there are ways to trigger such crafted requests even if an attacker does not have direct connectivity to a vulnerable devices. For example, simply visiting a website can result in the compromise of any ZyXEL device that is reachable from the client system. Affected products include: NAS326 before firmware V5.21(AAZF.7)C0 NAS520 before firmware V5.21(AASZ.3)C0 NAS540 before firmware V5.21(AATB.4)C0 NAS542 before firmware V5.21(ABAG.4)C0 ZyXEL has made firmware updates available for NAS326, NAS520, NAS540, and NAS542 devices. Affected models that are end-of-support: NSA210, NSA220, NSA220+, NSA221, NSA310, NSA310S, NSA320, NSA320S, NSA325 and NSA325v2

What CISA says to do