Draytek · Draytek Vigor300B · CVE-2021-42911
**Name of the Vulnerable Software and Affected Versions**
DrayTek Vigor 2960 versions 1.5.1.3 and earlier
DrayTek Vigor 3900 versions 1.5.1.3 and earlier
DrayTek Vigor 300B versions 1.5.1.3 and earlier
**Description**
The issue is related to a Format String vulnerability in the mainfunction.cgi file of the DrayTek Vigor web interface. This vulnerability can be exploited by a remote attacker using a crafted HTTP message with a malformed QUERY STRING, potentially allowing the execution of arbitrary code.
**Recommendations**
For DrayTek Vigor 2960 version 1.5.1.3 and earlier, update to a version later than 1.5.1.3.
For DrayTek Vigor 3900 version 1.5.1.3 and earlier, update to a version later than 1.5.1.3.
For DrayTek Vigor 300B version 1.5.1.3 and earlier, update to a version later than 1.5.1.3.
As a temporary workaround, consider restricting access to the mainfunction.cgi file until a patch is available.