CVE-2021-44224 is a high-severity vulnerability found in Apache HTTP Server versions 2.4.7 through 2.4.51. This vulnerability allows a crafted URI sent to httpd configured as a forward proxy (with ProxyRequests on) to cause a crash due to a NULL pointer dereference. Furthermore, configurations that mix forward and reverse proxy declarations can allow requests to be directed to a declared Unix Domain Socket endpoint, leading to a potential Server Side Request Forgery (SSRF).
The CVSS score for this vulnerability is 8.2, indicating a high severity level. The attack vector is network-based, and the attack complexity is low, meaning that no special conditions are required to exploit this vulnerability. The risk to organizations includes unauthorized access to sensitive internal resources, making it critical for organizations to address this vulnerability promptly.
Organizations should prioritize patching immediately to mitigate the risks associated with this vulnerability. The publication date of this vulnerability was December 20, 2021. As of the latest data, there are no known exploits available, but the potential impact of an attack highlights the urgency for remediation.
The affected systems include Apache HTTP Server and various distributions that utilize this server, such as Fedora and Debian. Organizations using these systems must ensure they are running patched versions to avoid exploitation.
Vulnerability Details
The vulnerability described in CVE-2021-44224 is a high-severity issue affecting Apache HTTP Server. The official description states that it allows a crafted URI sent to httpd configured as a forward proxy (ProxyRequests on) to potentially cause a crash or direct requests to a Unix Domain Socket endpoint. The CVSS score of 8.2 reflects the serious nature of this vulnerability, as it can lead to significant availability impact.
The vulnerability is classified under CWE-476, which refers to NULL Pointer Dereference. This issue affects all versions of Apache HTTP Server from 2.4.7 up to 2.4.51 (inclusive).
Technical Analysis
The root cause of CVE-2021-44224 is a flaw in the handling of crafted URIs by the Apache HTTP Server when configured as a forward proxy. When ProxyRequests is enabled, an attacker can send specially crafted URIs that cause a NULL pointer dereference, leading to a crash. This vulnerability can also be exploited to achieve Server Side Request Forgery (SSRF) under certain configurations, allowing attackers to make unauthorized requests to internal services.
The attack vector for this vulnerability is network-based, requiring no user interaction and no privileges. Thus, it poses a significant risk to vulnerable systems, especially if they expose their proxy capabilities to the internet.
Risk & Impact Analysis
Risk to organizations includes potential crashes of the HTTP server, leading to downtime and loss of service availability. Additionally, if exploited for SSRF, it could allow attackers to access internal resources or services that should remain protected. The potential blast radius of this vulnerability is significant, particularly for organizations that utilize Apache HTTP Server in critical infrastructure.
Given the high CVSS score of 8.2, organizations are advised to address this vulnerability in their priority patch cycle. The EPSS score of 0.1096 indicates a relatively low probability of exploitation; however, the potential impacts warrant immediate attention.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
Apache HTTP Server versions from 2.4.7 up to 2.4.51 are affected by this vulnerability. Organizations using these versions should ensure they apply the necessary patches to mitigate potential risks.
Mitigation & Remediation
To mitigate the risks associated with CVE-2021-44224, organizations should prioritize patching their affected Apache HTTP Server installations immediately. The latest versions of Apache should be used to ensure vulnerabilities are addressed.
If immediate patching is not feasible, organizations should consider disabling ProxyRequests or implementing network controls to limit exposure to potential exploitation. Continuous monitoring for unusual activity or crashes related to the HTTP server should also be implemented.
For further information on patching and best practices, organizations can refer to resources on penetration testing and security assessment.
Detection Guidance
To detect potential exploitation of CVE-2021-44224, organizations should monitor server logs for unusual request patterns that may indicate an attempt to exploit the vulnerability. Look for repeated access attempts to URI paths that are not standard for your applications.
Additionally, monitoring for abnormal crashes in the HTTP server can provide insights into potential exploitation attempts.
AppSecure Threat Intelligence Insight
The vulnerability represented by CVE-2021-44224 highlights the ongoing challenges associated with misconfigurations in server environments. As organizations increasingly rely on web services, the potential for exploitative behaviors against misconfigured services grows.
Security teams should take this as an opportunity to review their server configurations and ensure that unnecessary proxy functionalities are disabled unless explicitly required.
For further insights and guidance on maintaining secure server environments, organizations are encouraged to explore resources on penetration testing methodology and vulnerability management programs to strengthen their cybersecurity posture.
By remaining vigilant and proactive in their approach to vulnerabilities like CVE-2021-44224, organizations can mitigate risks and safeguard their critical assets.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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