CVE-2021-23840 is a high-severity vulnerability identified in OpenSSL, which allows for potential application crashes or erratic behavior. This vulnerability arises from calls to EVP_CipherUpdate, EVP_EncryptUpdate, and EVP_DecryptUpdate, where the output length argument may overflow under specific conditions. The underlying issue occurs when the input length approaches the maximum permissible length for an integer on the platform. When this overflow occurs, the function call returns a success value of 1, but the output length becomes negative.
The implications of this vulnerability are significant, as it may lead to unexpected application behavior or crashes, affecting the reliability of systems that rely on OpenSSL for cryptographic functions. With a CVSS score of 7.5, this vulnerability is classified as high severity, indicating a substantial risk to organizations. Notably, it affects versions 1.1.1i and below, necessitating immediate attention from users.
Organizations using OpenSSL should prioritize upgrading to version 1.1.1j or 1.0.2y for those on the 1.0.2 branch, as these versions include crucial fixes. The urgency of this update is underscored by the fact that all versions prior to these updates are vulnerable. Given the potential for exploitation, organizations are advised to address this issue in their patching cycles as soon as possible.
In summary, CVE-2021-23840 presents a notable risk, and organizations utilizing affected versions of OpenSSL must take immediate action to mitigate the associated vulnerabilities.
Vulnerability Details
This vulnerability allows for output length overflow, specifically in OpenSSL's cryptographic functions. The CVSS score of 7.5 indicates high severity, meaning the vulnerability is significant. The affected products include OpenSSL versions 1.1.1i and below. The issue was published on February 16, 2021, and is classified under CWE-190.
Technical Analysis
The root cause of CVE-2021-23840 is an integer overflow that occurs during cryptographic function calls. The attack vector is network-based, and the complexity is low, requiring no privileges or user interaction. The availability impact is high, as the overflow can lead to application crashes. There is no confidentiality or integrity impact reported.
Risk & Impact Analysis
The risk to organizations includes potential application crashes and unpredictable behavior, which could lead to service disruptions. Given the widespread use of OpenSSL, the blast radius of this vulnerability could be substantial, impacting numerous applications and services. The urgency for remediation is high, necessitating immediate patching to prevent exploitation.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
Affected versions include OpenSSL 1.1.1i and below, and OpenSSL 1.0.2x and below. Users should upgrade to OpenSSL 1.1.1j or 1.0.2y. If version information is missing, refer to vendor documentation for specific updates.
Mitigation & Remediation
Organizations should upgrade to OpenSSL 1.1.1j or 1.0.2y if they are using affected versions. If immediate patching is not possible, consider implementing workarounds such as disabling certain functionalities that rely on the affected functions. Additionally, configuration hardening and network controls can help mitigate the risks associated with this vulnerability. Monitoring for abnormal application behavior is also recommended.
For further details on penetration testing services that can assist in validating the effectiveness of these updates, organizations can refer to penetration testing to ensure proper implementation.
Detection Guidance
Organizations should monitor logs for indicators of unusual behavior, particularly around cryptographic operations. Behavioral anomalies, such as unexpected application crashes or incorrect outputs, may indicate exploitation attempts. Consider establishing network signatures to detect potential exploits targeting this vulnerability.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-23840 reflects the ongoing challenges in maintaining secure cryptographic libraries. This vulnerability illustrates the importance of thorough testing and validation of cryptographic operations. Security teams should prioritize regular updates and adopt a proactive stance toward vulnerability management.
For deeper insights into vulnerability management, organizations can explore our blog on vulnerability management program design, as well as our guide on penetration testing methodology for ensuring robust security measures.
Finally, organizations should review strategies for incident response and remediation to ensure they are prepared to address vulnerabilities like CVE-2021-23840 effectively.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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