Overview
The vulnerability CVE-2025-40916 is a critical cybersecurity issue that affects the Mojolicious::Plugin::CaptchaPNG version 1.05 for Perl. This vulnerability is primarily related to the weak random number source used for generating the captcha. The importance of this issue is underscored by the potential for system compromise or data leakage, which can have severe ramifications for any system reliant on this software plugin. It is therefore crucial for developers and system administrators to understand the nature of this vulnerability and to implement necessary mitigation strategies to secure their systems.
Vulnerability Summary
CVE ID: CVE-2025-40916
Severity: Critical (CVSS: 9.1)
Attack Vector: Network
Privileges Required: None
User Interaction: Required
Impact: System compromise and potential data leakage
Affected Products
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Product | Affected Versions
Mojolicious::Plugin::CaptchaPNG | 1.05
How the Exploit Works
The CVE-2025-40916 exploit hinges on the Mojolicious::Plugin::CaptchaPNG’s use of a weak random number source, specifically the built-in rand() function. This function is responsible for generating the captcha text and image noise. However, its inherent insecurity lies in its predictability, which can be exploited by an attacker to bypass the captcha verification process. With successful prediction and bypass, an attacker could potentially gain unauthorized access to system resources and data.
Conceptual Example Code
The following is a conceptual representation of how the vulnerability might be exploited. In this case, an attacker might use a sequence of known or predicted random numbers to bypass the captcha:
use Mojolicious::Lite;
use Mojolicious::Plugin::CaptchaPNG;
my $c = captcha png => {
width => 300,
height => 100,
len => 6,
lines => 10,
particles => 200,
};
# Here, the attacker predicts the next number in the sequence
my $predicted_captcha = predict_next_rand($c->random);
# The attacker then sends this predicted captcha as a response
send_captcha_response($predicted_captcha);
# If the prediction is correct, captcha verification is bypassed
if (verify_captcha($predicted_captcha)) {
# The attacker gains unauthorized access
access_system_resources();
}Keep in mind that this is a conceptual example and actual implementation may vary based on the specific context and the attacker’s knowledge of the system’s random number generation process.