CVE-2021-26691 is a critical vulnerability affecting Apache HTTP Server versions 2.4.0 to 2.4.46. This vulnerability allows a specially crafted SessionHeader sent by an origin server to cause a heap overflow. The severity of this vulnerability is underscored by its CVSS score of 9.8, classified as critical. This situation necessitates immediate attention from security teams to mitigate potential impacts.
Risk to organizations includes the potential for unauthorized access to sensitive data, service disruptions, and a compromised system integrity. The vulnerability is exploitable over the network with a low attack complexity and does not require user interaction. This highlights the urgency for organizations to prioritize patching immediately.
As of now, there are no public exploits confirmed for this vulnerability, but it’s crucial to monitor the situation closely. The Apache Software Foundation has released advisories regarding this vulnerability, emphasizing the need for affected users to upgrade to the latest versions.
Organizations utilizing Apache HTTP Server versions within the affected range should assess their environments and apply relevant patches as a part of their security protocols. Failure to address this vulnerability could expose them to severe risks.
Vulnerability Details
The official description states that this vulnerability allows a specially crafted SessionHeader sent by an origin server to cause a heap overflow in Apache HTTP Server versions 2.4.0 to 2.4.46. It falls under the CWE classifications of CWE-122 and CWE-787, indicating issues related to heap overflow and improper handling of data. The publication date for this vulnerability was June 10, 2021.
With a CVSS score of 9.8, the impacts of this vulnerability are classified as high in terms of confidentiality, integrity, and availability. The associated attack vector is network-based, indicating that an attacker could exploit this vulnerability remotely.
Technical Analysis
The root cause of CVE-2021-26691 is a flaw in how the Apache HTTP Server processes SessionHeaders. Attackers may leverage this flaw to inject malicious data, leading to a heap overflow condition. This vulnerability requires no privileges and does not necessitate user interaction, making it particularly dangerous.
The attack complexity is rated as low, enabling attackers to execute successful exploits with minimal effort. The high impact on confidentiality, integrity, and availability further complicates the threat landscape for organizations using affected versions.
Risk & Impact Analysis
Real-world deployment risks associated with this vulnerability are significant. Organizations that fail to patch their Apache HTTP Servers are exposed to a wide array of potential impacts, including data breaches and service outages. The blast radius is considerable, given the critical nature of web servers in application architectures.
The urgency for patching is critical, as this vulnerability allows for easy exploitation. Organizations should address this vulnerability in their priority patch cycle to mitigate risks effectively.
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerability affects Apache HTTP Server versions 2.4.0 to 2.4.46 and various products including Debian Linux 9.0 and 10.0, Fedora 34 and 35, and several Oracle products. Organizations should consider all versions prior to vendor patches as vulnerable.
Mitigation & Remediation
Organizations should prioritize applying security patches to their affected Apache HTTP Server installations. For those unable to immediately patch, consider implementing workarounds such as restricting access to vulnerable services and enhancing monitoring to detect any unusual activity. Additional measures can include configuration hardening and network controls to limit exposure.
For detailed guidance on effective penetration testing to validate the security posture of your systems, organizations can refer to penetration testing services that can help identify similar weaknesses.
Detection Guidance
Monitoring for anomalies in server behavior, such as unexpected service outages or memory usage spikes, can be crucial for early detection of exploitation attempts. Organizations should also look for unusual patterns in log files that may indicate a successful attack or attempted compromise.
AppSecure Threat Intelligence Insight
CVE-2021-26691 reflects a concerning trend in web server vulnerabilities where attackers exploit memory management flaws. Security teams must remain vigilant and proactive in their defenses. For in-depth strategies on vulnerability management, organizations may explore resources on vulnerability management programs. Additionally, implementing penetration testing methodologies can help ensure that similar vulnerabilities are identified and mitigated promptly.
Finally, organizations should stay informed about emerging threats through ongoing education and by reviewing API penetration testing insights to understand the evolving landscape of vulnerabilities.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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