TOTOLINK - Authentication Bypass (CVE-2019-19825)

CVE-2019-19825 is a critical vulnerability in certain TOTOLINK Realtek SDK-based routers that allows attackers to bypass CAPTCHA protections by retrieving the CAPTCHA text via a crafted POST request. This flaw enables remote attackers to automate login attempts and, once valid credentials are obtained, perform unauthorized router actions through HTTP requests with Basic Authentication. The vulnerability exposes affected devices to risks such as unauthorized configuration changes and potential network compromise.

CrowdSec has been tracking this vulnerability and its exploits since 10th of December 2025.

Data from the CrowdSec community indicates that exploitation of CVE-2019-19825 is highly selective and intelligence-driven. Threat actors use advanced reconnaissance and carefully choose their targets, often as part of sophisticated campaigns or advanced persistent threat operations. Data from the CrowdSec community also indicates a gradual decrease in attacks targeting CVE-2019-19825. While still present in the wild, exploitation levels have dropped noticeably week-over-week. This may signal that the vulnerability is becoming less relevant or that defenses are improving fast enough for attackers to lose interest.

Attackers exploit the CAPTCHA bypass by sending a POST request with the payload {"topicurl":"setting/getSanvas"} to the /boafrm/formLogin endpoint on TOTOLINK and Realtek-based routers, allowing them to retrieve the CAPTCHA value and facilitate unauthorized access.