CVE-2025-3666: A vulnerability was found in TOTOLINK A3700R 9.1.2u.5822_B20200513 and classified as critical

This week

MEDIUM 5.3REMOTEMITIGATE

CVE-2025-3666 is a medium-severity flaw (CVSS 5.3) affecting a3700r firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A vulnerability was found in TOTOLINK A3700R 9.1.2u.5822_B20200513 and classified as critical. Affected by this issue is the function setDdnsCfg of the file /cgi-bin/cstecgi.cgi. The manipulation leads to improper access controls. The attack may be launched remotely. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.

Why this priority

Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.6% (top 50%)
CISA exploited list	No
Weakness	CWE-266, CWE-284
Published	2025-04-16
Last modified	2026-06-17

Publisher (CNA): VulDB · Vendor: totolink

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-04-16 04:15 UTCPublished CVE record published
2026-06-17 09:20 UTCUpdated Record last modified

totolink a3700r firmware MITIGATE

Affected: 9.1.2u.5822_b20200513

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.1.2u.5822_b20200513

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-3666?

a3700r firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-3666 being exploited?

CVE-2025-3666 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-3666 affect?

CVE-2025-3666 affects a3700r firmware. Severity is medium (CVSS 5.3). A vulnerability was found in TOTOLINK A3700R 9.1.2u.5822_B20200513 and classified as critical. Affected by this issue is the function setDdnsCfg of the file /cgi-bin/cstecgi.cgi. The manipulation leads to improper access controls. The attac

How urgent is CVE-2025-3666?

Priority 41/100. Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-1143 HIGH 8.8 MITIGATE A weakness has been identified in TOTOLINK A3700R 9.1.2u.5822_B20200513
CVE-2025-3675 MEDIUM 5.3 MITIGATE A vulnerability was found in TOTOLINK A3700R 9.1.2u.5822_B20200513
CVE-2025-3674 MEDIUM 5.3 MITIGATE A vulnerability was found in TOTOLINK A3700R 9.1.2u.5822_B20200513
CVE-2025-3668 MEDIUM 5.3 MITIGATE A vulnerability was found in TOTOLINK A3700R 9.1.2u.5822_B20200513
CVE-2025-3667 MEDIUM 5.3 MITIGATE A vulnerability was found in TOTOLINK A3700R 9.1.2u.5822_B20200513

References

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