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CRITICAL

CVE-2021-42911

CVSS v3

9.8

CRITICAL

EPSS Score

3.5 %

exploit probability, as of 2026-10-19

CISA KEV

No

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2021-42911 yet.

Full record on NVD

Description

A Format String 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 in the mainfunction.cgi file via a crafted HTTP message containing malformed QUERY STRING, which could let a remote malicious user execute arbitrary code.

Technical details

Published
2022-03-29

Frequently asked questions

What is CVE-2021-42911?

A Format String 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 in the mainfunction.cgi file via a crafted HTTP message containing malformed QUERY STRING, which could let a remote malicious user execute arbitrary code.

Is CVE-2021-42911 actively exploited?

Active exploitation of CVE-2021-42911 has not been confirmed. Its EPSS score was 3.5% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-42911?

CVE-2021-42911 has a CVSS v3 base score of 9.8 (CRITICAL severity).

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