CVE-2021-4242 | Sapido BR270n/BRC76n/GR297/RB1732 syscmd.htm os command injection

Exp

A vulnerability was found in Sapido BR270n, BRC76n, GR297 and RB1732 and classified as critical. Affected by this issue is some unknown functionality of the file ip/syscmd.htm. The manipulation leads to os command injection. The attack may be launched remotely. The exploit has been disclosed to the public and may be used. The identifier of this vulnerability is VDB-214592.

Published: 2022-11-30 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-4242 is rated High Exploit Risk (74/100): CVSS Medium severity, with high exploitation likelihood (EPSS 11.52%, 94th percentile). 2 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.03% over the last day, indicating growing attacker interest. 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-2021-4242

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

Exploit prediction scoring system (EPSS) score for CVE-2021-4242

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 2026-05-26 10.48% 11.52% +1.03%
2 2025-12-17 3.48% 10.48% +7.00%
3 2025-12-03 — 3.48% —

Full EPSS history (20 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-4242

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.3 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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:L)
A normal user session is enough; they don’t have to be admin.
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:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.8 3.4 [email protected]
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
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:L)
A normal user session is enough; they don’t have to be admin.
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]

Weakness enumeration for CVE-2021-4242

Affected software / configurations for CVE-2021-4242

Vendor Product Version Raw CPE
sapido br270n_firmware 2.1.03 cpe:2.3:o:sapido:br270n_firmware:2.1.03:*:*:*:*:*:*:*
sapido brc76n_firmware 2.1.03 cpe:2.3:o:sapido:brc76n_firmware:2.1.03:*:*:*:*:*:*:*
sapido gr297n_firmware 2.1.3 cpe:2.3:o:sapido:gr297n_firmware:2.1.3:*:*:*:*:*:*:*
sapido rb-1732_firmware 2.0.43 cpe:2.3:o:sapido:rb-1732_firmware:2.0.43:*:*:*:*:*:*:*

References for CVE-2021-4242

cvelogic Threat Intelligence