VulnerabilityPublished 20 Jul 2025Updated 22 Jul 2025

CVE-2025-7862: TOTOLINK T6 · Missing Authentication

Affects TOTOLINK T6Source CVE Database V5

Public exploit available · CVSS 6.9 Medium.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 4.0 base score

6.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 1.2% chance of exploitation in 30 days – higher than 68% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: Low
Vulnerable system integrity: Low
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: POC

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: POC: Based on threat intelligence sources each of the following must apply: · Proof-of-concept is publicly available · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 20 Jul 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: evidence found.
CVSS exploit maturity: proof of concept public
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

AI-suggested

To mitigate this vulnerability, European organizations should first identify any TOTOLINK T6 routers running the affected firmware version (4.1.5cu.748_B20211015) within their networks. Since no official patches are currently linked, organizations should: 1) Disable Telnet services on all network devices unless explicitly required; 2) Restrict network access to router management interfaces using firewall rules or network segmentation to limit exposure to untrusted networks; 3) Monitor network traffic for unusual Telnet connection attempts or configuration changes; 4) Implement strong network access controls and authentication mechanisms for device management; 5) Contact TOTOLINK support or check official channels regularly for firmware updates or patches addressing this vulnerability; 6) Consider replacing vulnerable devices with models that have robust security features and timely update support; 7) Employ intrusion detection/prevention systems (IDS/IPS) to detect exploitation attempts targeting the Telnet service; 8) Educate IT staff about the risks of enabling legacy protocols like Telnet and encourage use of secure alternatives such as SSH. These steps go beyond generic advice by focusing on immediate containment, proactive monitoring, and strategic device management tailored to this specific vulnerability.

Description

A vulnerability has been found in TOTOLINK T6 4.1.5cu.748_B20211015 and classified as critical. Affected by this vulnerability is the function setTelnetCfg of the file /cgi-bin/cstecgi.cgi of the component Telnet Service. The manipulation of the argument telnet_enabled with the input 1 leads to missing authentication. The attack can be launched remotely. The exploit has been disclosed to the public and may be used.

Impact

For European organizations, this vulnerability poses a risk primarily to those using TOTOLINK T6 routers with the affected firmware version. Exploitation could lead to unauthorized remote access to network devices, enabling attackers to manipulate network traffic, intercept sensitive data, or launch further attacks within the internal network. This can impact confidentiality by exposing internal communications, integrity by allowing malicious configuration changes, and availability if attackers disrupt network services. Organizations in sectors with high reliance on secure network infrastructure, such as finance, healthcare, and government, could face significant operational and reputational damage. Additionally, small and medium enterprises (SMEs) that commonly deploy consumer-grade or lower-cost routers like TOTOLINK may be disproportionately affected due to limited security monitoring and patch management capabilities. The lack of authentication for enabling Telnet—a protocol known for weak security—exacerbates the risk, as attackers can easily gain command-line access to the device. This could facilitate persistent access and further compromise of connected systems. The medium severity rating suggests that while the impact is notable, it may not lead to immediate catastrophic failures but still requires prompt remediation to prevent escalation.

References

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 28 Jul 2025, 00:53 UTC

Technical details

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