CVE-2021-20139

Exp

An unauthenticated command injection vulnerability exists in the parameters of operation 3 in the controller_server service on Gryphon Tower routers. An unauthenticated remote attacker on the same network can execute commands as root on the device by sending a specially crafted malicious packet to the controller_server service on port 9999.

Published: 2021-12-09 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-20139 is rated High Exploit Risk (77.6/100): CVSS High severity, with medium exploitation likelihood (EPSS 3.98%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-20139

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-20139

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 7.77% 3.98% -3.78%
2 2025-11-21 5.25% 7.77% +2.52%
3 2025-11-18 — 5.25% —

Full EPSS history (12 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-20139

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:A)
Attacker has to be nearby on the network—same office, same link, that vibe—not the whole wide internet.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
8.3 2.0 HIGH
AV:A/AC:L/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:A)
Requires access to an adjacent network segment.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 6.5 10.0 [email protected]

Weakness enumeration for CVE-2021-20139

Affected software / configurations for CVE-2021-20139

Vendor Product Version Raw CPE
gryphonconnect gryphon_tower_firmware <= 04.0004.12 cpe:2.3:o:gryphonconnect:gryphon_tower_firmware:*:*:*:*:*:*:*:*

References for CVE-2021-20139

cvelogic Threat Intelligence