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CVE-2020-9054

98
FAUCET Score

CVE-2020-9054 is a critical pre-authentication command injection vulnerability affecting multiple ZyXEL Network-Attached Storage (NAS) devices running firmware version 5.21 and earlier. This flaw allows a remote, unauthenticated attacker to execute arbitrary code with root privileges by manipulating the username parameter in weblogin.cgi. The vulnerability carries a CVSS score of 9.8 (Critical) due to its network-based attack vector, low complexity, and complete compromise of confidentiality, integrity, and availability. Successful exploitation can lead to full device control, even through indirect means like visiting a malicious website. This vulnerability is actively exploited in the wild, as confirmed by its presence in the CISA KEV catalog and its high EPSS score. While no Metasploit or ExploitDB modules are publicly available, Nuclei templates exist, and it has garnered significant community discussion and media coverage, including its use in Mirai and BotenaGo botnet strains.

Impacted Technologies

VendorProductVersion(s)CPE
< 5.21\(aazf.7\)c0CPE matchmatch criteria
cpe:2.3:o:zyxel:nas326_firmware:*:*:*:*:*:*:*:*
< 5.21\(aasz.3\)c0CPE matchmatch criteria
cpe:2.3:o:zyxel:nas520_firmware:*:*:*:*:*:*:*:*
< 5.21\(aatb.4\)c0CPE matchmatch criteria
cpe:2.3:o:zyxel:nas540_firmware:*:*:*:*:*:*:*:*
< 5.21\(abag.4\)c0CPE matchmatch criteria
cpe:2.3:o:zyxel:nas542_firmware:*:*:*:*:*:*:*:*
>= 4.35, < 4.35\(abps.3\)c0CPE matchmatch criteria
cpe:2.3:o:zyxel:atp100_firmware:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
99.99%
Probability of exploitation in next 30 days
EPSS Percentile
100.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
Added to KEV · Mar 25, 2022
Nuclei: CVE-2020-9054 · May 1, 2021
This CVE's current EPSS score of 0.9999 is in the 100th percentile among its peer group of 36,833 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

cisa.gov / known-exploited-vulnerabilities-catalog
US Government Resource
cwe.mitre.org / data/definitions/78.html
Third Party Advisory
kb.cert.org / artifacts/cve-2020-9054.html
Third Party AdvisoryUS Government Resource
kb.cert.org / vuls/id/498544
Third Party AdvisoryUS Government Resource
krebsonsecurity.com / 2020/02/zyxel-fixes-0day-in-network-storage-devices
ExploitThird Party Advisory
zyxel.com / support/remote-code-execution-vulnerability-of-NAS-products.shtml
Vendor Advisory