CVE-2018-14596 in wancms
Summary
by MITRE
wancms 1.0 through 5.0 allows remote attackers to cause a denial of service (resource consumption) via a checkcode (aka verification code) URI in which the values of font_size, width, and height are large numbers.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 03/10/2020
The vulnerability identified as CVE-2018-14596 affects wancms versions 1.0 through 5.0 and represents a denial of service flaw that can be exploited by remote attackers through manipulation of the checkcode URI parameter. This issue falls under the category of resource consumption attacks where malicious actors can exhaust system resources by submitting carefully crafted parameters that cause the application to consume excessive computational or memory resources. The vulnerability specifically targets the verification code generation functionality within the content management system, which is typically used to prevent automated bot submissions and ensure legitimate user interactions.
The technical flaw manifests when attackers manipulate three specific parameters within the checkcode URI: font_size, width, and height. These parameters control the visual characteristics of the generated verification codes that users must input to complete various actions within the CMS. When these parameters are set to extremely large numerical values, the application processes these inputs without proper validation or bounds checking, leading to exponential resource consumption. The system attempts to render verification codes with dimensions and font sizes that are far beyond reasonable limits, causing memory allocation issues and processing overhead that can quickly overwhelm system resources. This type of vulnerability is classified as a resource exhaustion attack and aligns with CWE-400 which specifically addresses "Uncontrolled Resource Consumption" in software systems.
The operational impact of this vulnerability extends beyond simple service disruption to potentially affect the entire availability of the CMS platform. Attackers can exploit this flaw to consume CPU cycles and memory resources at an alarming rate, potentially causing the web server to become unresponsive or crash entirely. The effects can cascade to impact other services running on the same infrastructure, creating broader system instability. Given that verification code generation is a common feature in web applications, this vulnerability could be exploited to target multiple CMS instances simultaneously, making it particularly dangerous for organizations running multiple web applications or those with high traffic volumes. The attack can be executed without authentication requirements, making it an attractive vector for denial of service attacks that can be launched from any internet-connected device.
Mitigation strategies for CVE-2018-14596 should focus on implementing proper input validation and parameter sanitization within the checkcode generation functionality. Organizations should establish strict bounds checking for font_size, width, and height parameters to prevent values from exceeding reasonable thresholds typically associated with standard verification code generation. This approach aligns with the principle of least privilege and defense in depth strategies recommended by security frameworks. Additionally, implementing rate limiting mechanisms and monitoring for unusual parameter values can help detect and prevent exploitation attempts. The solution should also include proper error handling and resource management to ensure that even if malicious input is received, the system can gracefully handle it without consuming excessive resources. Security teams should consider implementing application-level firewalls or web application firewalls that can detect and block requests containing suspicious parameter combinations. This vulnerability demonstrates the importance of validating all user inputs and implementing proper resource management practices, which are core tenets of the OWASP Top Ten security risks and align with ATT&CK technique T1499 which covers resource exhaustion attacks. Organizations should also ensure that their CMS versions are kept up to date with the latest security patches and that proper security testing is conducted to identify similar vulnerabilities in other components of their web applications.