High severity · published Aug 6, 2020
CVE-2020-13364
A backdoor in certain Zyxel products allows remote TELNET access via a CGI script
8.8
CVSS
1.2%
EPSS
No
On KEV
Description
A backdoor in certain Zyxel products allows remote TELNET access via a CGI script. This affects NAS520 V5.21(AASZ.4)C0, V5.21(AASZ.0)C0, V5.11(AASZ.3)C0, and V5.11(AASZ.0)C0; NAS542 V5.11(ABAG.0)C0, V5.20(ABAG.1)C0, and V5.21(ABAG.3)C0; NSA325 v2_V4.81(AALS.0)C0 and V4.81(AAAJ.1)C0; NSA310 4.22(AFK.0)C0 and 4.22(AFK.1)C0; NAS326 V5.21(AAZF.8)C0, V5.11(AAZF.4)C0, V5.11(AAZF.2)C0, and V5.11(AAZF.3)C0; NSA310S V4.75(AALH.2)C0; NSA320S V4.75(AANV.2)C0 and V4.75(AANV.1)C0; NSA221 V4.41(AFM.1)C0; and NAS540 V5.21(AATB.5)C0 and V5.21(AATB.3)C0.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.2% · higher than 67% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NF
Nas326 Firmware · Zyxel
before v5.21\(aazf.9\)c0 · source: NVD
NF
Nas520 Firmware · Zyxel
before v5.21\(aasz.5\)c0 · source: NVD
NF
Nas540 Firmware · Zyxel
before v5.21\(aatb.6\)c0 · source: NVD
NF
Nas542 Firmware · Zyxel
before v5.21\(abag.6\)c0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-13364
CVE.org
https://www.cve.org/CVERecord?id=CVE-2020-13364
Vendor Advisory
https://www.zyxel.com/support/Zyxel-security-advisory-for-NAS-remote-access-vulnerability.shtml
Vendor Advisory
https://www.zyxel.com/us/en/support/security_advisories.shtml
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