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 Vig…
- Is it exploited?
Reported, not confirmed by CISA. VulnCheck KEV lists it as exploited in the wild. CISA has not added it to its Known Exploited Vulnerabilities catalog as of .
VulnCheck KEV lists it since . VulnCheck's own honeypots also recorded exploitation attempts.
- How likely is exploitation in the next 30 days?
- 3.5%
EPSS score, percentile 89.4 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- Not scored
The CVE record carries no CVSS score.
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
No patch or vendor advisory is listed in the CVE record. Check the vendor's advisories.
- Which versions are affected?
Not stated. The CVE record gives vendor and product as “n/a” and the version as “unspecified”.
Source: CISA KEV 2026.11.10, as of ; VulnCheck KEV, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
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.
Source: CVE List, as of . About the data.
What to do
Advisories and patches
No patch, vendor advisory or mitigation is listed in the CVE record. Check the vendor's own security advisories for a fix, and compare your version with the affected versions below.
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
The CVE record does not name affected products or versions: vendor and product are “n/a” and the version is “unspecified”.
Source: CVE List, as of . About the data.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| CVE record last updated |