In PHP versions 7.4.x below 7.4.28, 8.0.x below 8.0.16, and 8.1.x below 8.1.3, a vulnerability allows for the potential exploitation of memory management failures. This vulnerability allows the use of the FILTER_VALIDATE_FLOAT filter with min/max limits. If the filter fails, there is a possibility to trigger use of allocated memory after free, which can result in crashes and potentially in overwrite of other memory chunks and remote code execution (RCE).
The severity of this vulnerability is classified as high, with a CVSS score of 8.2. This indicates significant risk to organizations that utilize affected PHP versions, as it can lead to unauthorized access and data manipulation. Organizations should prioritize patching immediately.
The vulnerability has been modified since its initial disclosure, and while no public exploit has been confirmed, the potential for exploitation remains a concern. The urgency for defenders to address this vulnerability is underscored by its potential impact on system integrity and availability.
Organizations using vulnerable versions of PHP should assess their systems for the presence of this vulnerability and deploy the necessary patches as soon as possible.
Vulnerability Details
The official description of the vulnerability details a use-after-free condition triggered by the FILTER_VALIDATE_FLOAT function when it fails to validate inputs against defined min/max limits. This vulnerability is classified under CWE-416, indicative of a memory management error.
The CVSS score from NVD is 9.8, indicating critical severity, while the score from PHP is 8.2, categorized as high. The difference in scoring reflects the potential impact and exploitability of the vulnerability on various systems.
The vulnerability was published on February 27, 2022, and affects all versions of PHP prior to the specified patches.
Technical Analysis
The root cause of this vulnerability stems from improper memory management when the FILTER_VALIDATE_FLOAT filter fails. The attack vector is network-based, allowing remote attackers to exploit this flaw without the need for user interaction, and with no privileges required.
The attack complexity is considered low, making it easier for attackers to exploit the vulnerability. The confidentiality impact is none, while the integrity impact is high, and there is a low availability impact. This means that while data confidentiality is not compromised, the integrity of data can be manipulated, posing significant risks to applications relying on PHP.
Risk & Impact Analysis
The real-world risk associated with this vulnerability is substantial as it affects widely used PHP versions. Vulnerable applications can be manipulated to execute arbitrary code, leading to data breaches and unauthorized access. The potential blast radius includes any application or service relying on the affected PHP versions, which can result in widespread compromise.
Given the CVSS score of 9.8, organizations should address this vulnerability in their priority patch cycle. The vulnerability's presence in critical environments enhances the urgency for remediation to prevent exploitation.
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The following versions of PHP are affected by this vulnerability: 7.4.x prior to 7.4.28, 8.0.x prior to 8.0.16, and 8.1.x prior to 8.1.3. Organizations using these versions should ensure they are upgraded to the patched versions.
Mitigation & Remediation
Organizations should prioritize patching vulnerable PHP versions to mitigate this risk. The recommended remediation is to upgrade to PHP 7.4.28, 8.0.16, or 8.1.3, respectively. If immediate patching is not feasible, consider implementing workarounds such as restricting access to affected applications and employing network controls.
Additionally, organizations may want to evaluate their security posture by utilizing continuous penetration testing to identify any similar weaknesses.
Detection Guidance
To monitor for potential exploitation of this vulnerability, organizations should implement logging mechanisms that capture abnormal behaviors related to PHP filter functions. Look for signs of unexpected crashes or memory usage spikes that could indicate an attack.
Network signatures should also be established to detect attempts to interact with vulnerable applications, and system changes should be closely monitored for unauthorized modifications.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-21708 lies in its demonstration of how memory management flaws in widely-used technologies can lead to severe security vulnerabilities. As organizations continue to adopt PHP in various applications, the potential for exploitation remains a persistent threat.
Security teams must recognize the patterns of vulnerabilities that arise from improper input validation and memory management. This incident serves as a reminder of the critical importance of adhering to secure coding practices.
To enhance defenses against similar threats, consider reviewing the following resources: penetration testing methodology, vulnerability management program design, and web application penetration testing best practices to strengthen overall security posture.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
.webp)