How severe is CVE-2021-43118?

CVE-2021-43118 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-43118 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 35% (98th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43118?

CVE-2021-43118 primarily affects Draytek Vigor2960 Firmware. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-43118?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-43118 published?

CVE-2021-43118 was published on 2022-03-29 and last updated on 2026-06-17.

CVE-2021-43118

CVE-2021-43118 is a critical-severity vulnerability in Draytek Vigor2960 Firmware with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 35% places it in the 98th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-77.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 35% (98th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-77
Affected product: Draytek Vigor2960 Firmware
Published: 2022-03-29
Last modified: 2026-06-17

Description

A Remote Command Injection vulnerability exists in DrayTek Vigor 2960 1.5.1.3, DrayTek Vigor 3900 1.5.1.3, and DrayTek Vigor 300B 1.5.1.3 via a crafted HTTP message containing malformed QUERY STRING in mainfunction.cgi, which could let a remote malicious user execute arbitrary code.

Frequently asked questions

What is CVE-2021-43118?: A Remote Command Injection vulnerability exists in DrayTek Vigor 2960 1.5.1.3, DrayTek Vigor 3900 1.5.1.3, and DrayTek Vigor 300B 1.5.1.3 via a crafted HTTP message containing malformed QUERY STRING in mainfunction.cgi, which could let a remote malicious user execute arbitrary code.
How severe is CVE-2021-43118?: CVE-2021-43118 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-43118 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 35% (98th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43118?: CVE-2021-43118 primarily affects Draytek Vigor2960 Firmware. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-43118?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-43118 published?: CVE-2021-43118 was published on 2022-03-29 and last updated on 2026-06-17.

References

https://gist.github.com/Cossack9989/6034c077f46e4f06d0992e9f2fae7f26

Affected products (3)

cpe:2.3:o:draytek:vigor2960_firmware:1.5.1.3:*:*:*:*:*:*:*
cpe:2.3:o:draytek:vigor3900_firmware:1.5.1.3:*:*:*:*:*:*:*
cpe:2.3:o:draytek:vigor300b_firmware:1.5.1.3:*:*:*:*:*:*:*

More vulnerabilities in Draytek Vigor2960 Firmware

CVE-2021-42911 — Critical (CVSS 9.8): A Format String vulnerability exists in DrayTek Vigor 2960 <= 1.5.1.3, DrayTek Vigor 3900 <= 1.5.1.3, and DrayTek Vigor…
CVE-2020-15415 — Critical (CVSS 9.8): On DrayTek Vigor3900, Vigor2960, and Vigor300B devices before 1.5.1, cgi-bin/mainfunction.cgi/cvmcfgupload allows…
CVE-2020-14473 — Critical (CVSS 9.8): Stack-based buffer overflow vulnerability in Vigor3900, Vigor2960, and Vigor300B with firmware before 1.5.1.1.
CVE-2020-14472 — Critical (CVSS 9.8): On Draytek Vigor3900, Vigor2960, and Vigor 300B devices before 1.5.1.1, there are some command-injection…
CVE-2020-14993 — Critical (CVSS 9.8): A stack-based buffer overflow on DrayTek Vigor2960, Vigor3900, and Vigor300B devices before 1.5.1.1 allows remote…
CVE-2020-10828 — Critical (CVSS 9.8): A stack-based buffer overflow in cvmd on Draytek Vigor3900, Vigor2960, and Vigor300B devices before 1.5.1 allows remote…

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