Cyber Resilience

CVE-2025-67186

Memory Safety in Totolink A950Rg Firmware 4.1.2cu.5204_b20210112

Public PoCMemory Safety
Published
03 February 2026
Modified
10 February 2026
CVSS Score v3.1 9.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0069 50th percentile
Risk Priority 74 floored blend · peak EPSS

Summary

CVE-2025-67186 is a critical-severity Classic Buffer Overflow (CWE-120) vulnerability in Totolink A950Rg Firmware. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 50th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

TOTOLINK A950RG routers running firmware version V4.1.2cu.5204_B20210112 are affected by CVE-2025-67186, a buffer overflow vulnerability (CWE-120) in the setUrlFilterRules interface within the /lib/cste_modules/firewall.so library. The issue arises because the `url` parameter lacks proper length validation, enabling attackers to overflow the buffer. Published on 2026-02-03, this vulnerability carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating critical severity due to its potential for high-impact exploitation.

Remote attackers can exploit this vulnerability without authentication, privileges, or user interaction by sending specially crafted requests to the affected interface. Successful exploitation may result in arbitrary code execution on the device or denial of service, allowing full compromise of the router's functionality, including potential network pivoting or persistence in IoT environments.

Mitigation details are available in the primary advisory reference at https://github.com/SunnyYANGyaya/cuicuishark-sheep-fishIOT/blob/main/ToTolink/A950RG/5024-setUrlFliterRules-url-buffer.md, which likely includes technical analysis and proof-of-concept information for practitioners to assess and address the issue. No vendor patches are specified in available data.

EU & UK References

Vulnerability Data

TOTOLINK A950RG V4.1.2cu.5204_B20210112 contains a buffer overflow vulnerability in the setUrlFilterRules interface of /lib/cste_modules/firewall.so. The vulnerability occurs because the `url` parameter is not properly validated for length, allowing remote attackers to trigger a buffer overflow, potentially leading to arbitrary code…

more

execution or denial of service.

CWE(s)
CWE-120

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-67188Same product: Totolink A950Rg
CVE-2025-67189Same product: Totolink A950Rg
CVE-2025-67187Same product: Totolink A950Rg
CVE-2025-60699Same product: Totolink A950Rg
CVE-2025-45797Same product: Totolink A950Rg
CVE-2025-28025Same product: Totolink A950Rg
CVE-2025-28028Same product: Totolink A950Rg
CVE-2025-45800Same product: Totolink A950Rg
CVE-2025-45798Same product: Totolink A950Rg
CVE-2025-60702Same product: Totolink A950Rg

Affected Assets

totolink
a950rg firmware
4.1.2cu.5204_b20210112

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V5.2.1

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and analysis can find missing size checks before deployment.

SI-10 Information Input Validation good match

Input validation directly enforces size checks before buffer copies.

SA-8 Security and Privacy Engineering Principles partial match

Engineering principles require bounds checking and safe buffer handling in design.

SI-16 Memory Protection partial match

Memory protection limits the impact of an overflow once it occurs.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure development practices directly enforce bounds checking and input validation that prevent classic buffer overflows.

ID.RA-01 partial match
prevents

Vulnerability identification processes such as code review or scanning detect classic buffer overflows before exploitation.

PR.PS-02 partial match
prevents

Routine patching replaces vulnerable code containing unchecked buffer copies with corrected versions.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.28 Secure coding mostly match
prevents

Secure coding directly requires bounds-checked memory operations, addressing the root cause of CWE-120.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development and acceptance can detect buffer overflows through fuzzing and static analysis, though it does not prevent them at the source.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates processes that can include input validation and bounds checking to prevent buffer overflows.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify input-size validation and safe buffer handling to mitigate classic buffer overflows.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure system architecture and engineering principles promote defensive coding patterns that reduce the likelihood of unchecked buffer copies.

References