CVE-2021-4044 is a high-severity vulnerability in OpenSSL that affects the library's handling of certificate verification. Specifically, the issue arises when the function X509_verify_cert() returns a negative value, indicating an internal error. OpenSSL mishandles this return value, which can lead to an IO function not indicating success. This unexpected behavior can cause applications to respond incorrectly, potentially resulting in crashes or infinite loops.
The vulnerability is exacerbated by a separate bug in OpenSSL 3.0 that may cause X509_verify_cert() to indicate an internal error when processing certificate chains, particularly when the Subject Alternative Name extension is missing. This can happen even with valid chains, allowing attackers to induce unpredictable application behavior.
With a CVSS score of 7.5, this vulnerability poses a significant risk to organizations using affected OpenSSL versions. The urgency for defenders is high, as patching should be prioritized to prevent potential exploitation.
Organizations must address this vulnerability promptly to mitigate the risk of application failures and ensure stable operations.
Vulnerability Details
CVE-2021-4044 allows for improper verification of certificates due to mishandled return values from X509_verify_cert(). This can lead to serious consequences in various applications, including crashes. The vulnerability has been classified under CWE-835, indicating a potential flaw in the application's handling of error conditions.
The vulnerability was published on December 14, 2021, and affects OpenSSL versions prior to 3.0.1. The issue has been acknowledged and addressed in the subsequent patch, highlighting the importance of maintaining updated software.
Technical Analysis
The root cause of CVE-2021-4044 lies in the improper handling of error codes returned by the X509_verify_cert() function. An attacker could exploit this flaw by manipulating the certificate verification process, thereby causing unexpected behavior in applications that rely on OpenSSL for secure communications.
The attack vector is network-based, with low complexity and no privileges required for exploitation. User interaction is not necessary, making this vulnerability particularly concerning for many applications.
The impacts on availability are high, as compromised applications could become unresponsive or crash. There is no confidentiality or integrity impact associated with this vulnerability.
Risk & Impact Analysis
Organizations utilizing OpenSSL in their applications face serious risks due to CVE-2021-4044. The potential for application crashes or infinite loops can lead to significant operational disruptions. As many applications do not expect the SSL_ERROR_WANT_RETRY_VERIFY return value, the likelihood of encountering unexpected failures is high.
The blast radius for this vulnerability is substantial, especially for services relying on OpenSSL for secure communications. Organizations must evaluate their exposure and prioritize remediation efforts to mitigate this risk.
Given the high CVSS score of 7.5, immediate action is necessary. Organizations should prioritize patching OpenSSL to the latest version to protect against potential exploits.
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The vulnerable versions of OpenSSL include 3.0.0 and earlier, as well as certain versions of NetApp products such as cloud_backup and snapcenter. Organizations are advised to upgrade to OpenSSL 3.0.1 or later to mitigate this vulnerability.
Mitigation & Remediation
Organizations should prioritize patching OpenSSL to version 3.0.1 or later to remediate this vulnerability. If immediate upgrading is not possible, consider implementing configuration hardening and monitoring for unusual application behavior as interim measures.
For further assistance in securing your applications, organizations can utilize penetration testing services to validate the effectiveness of their security measures.
Detection Guidance
To detect potential exploitation of CVE-2021-4044, organizations should monitor logs for unusual application behavior, including unexpected error messages or application crashes. Additionally, network signatures indicating anomalies in SSL/TLS communications may serve as indicators of compromise.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-4044 lies in its demonstration of the complexities involved in certificate verification processes. This vulnerability underscores the necessity for developers to implement robust error handling to prevent similar issues in the future.
Security teams should take this opportunity to review their error handling practices and consider adopting best practices for application security. For further information on improving your security posture, consult our penetration testing methodology and the importance of maintaining updated security measures.
The patterns observed in CVE-2021-4044 are indicative of broader trends in application vulnerabilities, emphasizing the need for continuous monitoring and proactive defense strategies. For organizations utilizing OpenSSL or similar technologies, it is crucial to stay informed about emerging threats and vulnerabilities.
To further enhance your organization's security posture, consider exploring our vulnerability management program to identify and mitigate potential risks effectively.
Additionally, adopting a proactive approach by engaging in web application penetration testing can assist in uncovering similar vulnerabilities before they can be exploited.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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