Guessable CAPTCHA in AVideo - CVE-2026-40935
Published: November 11, 2026
Vulnerability identifier: #VU165905
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-40935
CWE-ID: CWE-804
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to bypass CAPTCHA protection in AVideo and automate account creation, password-reset spam, and unsolicited email.
The vulnerability exists due to attacker-controlled CAPTCHA length, case-insensitive comparison, and missing token invalidation after failed guesses in objects/getCaptcha.php and objects/captcha.php when generating and validating challenges. A remote attacker can request /objects/getCaptcha.php?ql=1 and submit up to 33 single-character guesses within the same session to bypass CAPTCHA checks on endpoints using Captcha::validation().
Affected software
AVideo
How to mitigate CVE-2026-40935
Install security update from vendor's website.
AVideo - update to 29.1.0