What is CVE-2021-26709?

CVE-2021-26709 is a critical-severity vulnerability in D-Link Dsl-320b-D1, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2021-04-07.

How severe is CVE-2021-26709?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in D-Link Dsl-320b-D1

CVE-2021-26709

D-Link DSL-320B-D1 devices through EU_1.25 are prone to multiple Stack-Based Buffer Overflows that allow unauthenticated remote attackers to take over a device via the login.xgi user and pass parameters. NOTE: This vulnerability only affects products that are no longer supported by the maintainer

Vulnerability class: Buffer Overflow

Published 2021-04-07 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.401 (98.6th percentile), scored 2026-09-30.

Moderate probability of exploitation in the next 30 days — watch for active exploitation reports. 99th percentile — 98.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.401 · newest: 0.401 · change: 0.000

Affected products

D-Link Dsl-320b-D1

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

www.dlink.com/en/security-bulletin (Vendor Advisory)
supportannouncement.us.dlink.com/announcement/publication.aspx (Vendor Advisory)
seclists.org/fulldisclosure/2021/Apr/15 (mailing-list, Mailing List, Third Party Advisory)
packetstormsecurity.com/files/162133/D-Link-DSL-320B-D1-Pre-Authentication-Buff… (Exploit, VDB Entry, Third Party Advisory)

Frequently asked questions

What is CVE-2021-26709?: CVE-2021-26709 is a critical-severity vulnerability in D-Link Dsl-320b-D1, classified under Out-of-bounds Write. CVSS score: 9.8/10. Published 2021-04-07.
How severe is CVE-2021-26709?: Critical severity. CVSS v3 base score is 9.8 out of 10.