Buffer overflow in Draytek Corporation Vigorswitch Fx2120

CVE-2026-71936

Multiple DrayTek VigorSwitch models contain a buffer overflow vulnerability in the sysreboot function. The vulnerability is caused by unsafe concatenation of split valueN data into a fixed-size buffer. A remote attacker can trigger this vulnerability via crafted input, causing a denial of service or potentially executing arbitrary commands. Exploitation requires valid administrative credentials for the device's web management interface.

Vulnerability class: Buffer Overflow

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.007 (51.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-71936: held from 0.005 to 0.007.

EPSS over last 30 days · oldest: 0.005 · newest: 0.007 · change: +0.002

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-71936?
CVE-2026-71936 is a high-severity vulnerability in Draytek Corporation Vigorswitch Fx2120, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 7.2/10. Published 2026-08-24.
How severe is CVE-2026-71936?
High severity. CVSS v3 base score is 7.2 out of 10.