CVE-2021-3711 is a critical vulnerability affecting OpenSSL, specifically its SM2 decryption functionality. This flaw allows an attacker to exploit a buffer overflow condition during the decryption process, which could lead to arbitrary code execution, application crashes, or unauthorized data manipulation. The vulnerability has a CVSS score of 9.8, indicating its high severity and the urgent need for mitigation.
The risk to organizations includes potential unauthorized access to sensitive data and disruption of services due to application crashes. Exploitation can occur over a network, making it particularly critical for systems that utilize OpenSSL for cryptographic functions. Organizations using affected versions of OpenSSL are advised to address this vulnerability without delay.
The vulnerability was published on August 24, 2021, and is classified as a buffer overflow issue (CWE-120). It arises from a flaw in the SM2 decryption process that leads to insufficient buffer allocation, allowing an attacker to overflow the buffer by up to 62 bytes.
Organizations should prioritize patching immediately. The vulnerability has been addressed in OpenSSL version 1.1.1l, and it is crucial for all users to upgrade to this version or later to mitigate the risks associated with CVE-2021-3711.
Vulnerability Details
The official description of CVE-2021-3711 states that applications using the EVP_PKEY_decrypt() function to decrypt SM2 encrypted data may experience a buffer overflow. The first call to this function can return a buffer size that is smaller than required for the second call, leading to potential overflows if proper precautions are not taken.
This vulnerability is critical due to its high CVSS score of 9.8 and affects all versions of OpenSSL prior to 1.1.1l. The impact on confidentiality, integrity, and availability is significant, as attackers may exploit this flaw to manipulate application behavior or crash systems.
Technical Analysis
The root cause of this vulnerability is a flaw in the SM2 decryption implementation, where the buffer size calculation is incorrect. As a result, when the application calls EVP_PKEY_decrypt() a second time with a buffer that is too small, it can lead to a buffer overflow, allowing an attacker to overwrite adjacent memory locations.
The attack vector is network-based, with low complexity required for exploitation. No privileges or user interaction are needed, making this vulnerability particularly dangerous. The impacts on confidentiality, integrity, and availability are all high, as unauthorized data access and application crashes can occur.
Risk & Impact Analysis
Organizations utilizing OpenSSL in their applications face a real-world risk of exploitation that could lead to significant operational disruptions. The potential for data breaches and unauthorized access heightens the urgency for remediation. The blast radius is considerable, affecting any application dependent on vulnerable OpenSSL versions, and the urgency assessment is critical based on the CVSS score of 9.8.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | Yes |
Public PoC | Yes |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
CVE-2021-3711 affects all versions of OpenSSL from 1.1.1 to 1.1.1k. Users are urged to upgrade to OpenSSL version 1.1.1l or later. Additionally, the vulnerability impacts various products including Debian and NetApp solutions, among others.
Mitigation & Remediation
To remediate this vulnerability, organizations should immediately upgrade to OpenSSL version 1.1.1l or later. For those unable to apply the patch right away, consider implementing workarounds such as restricting access to applications that utilize vulnerable OpenSSL versions. Configuration hardening and network controls can also help mitigate potential exploitation. For detailed guidance, organizations may refer to our application security assessment services that can assist in evaluating the security posture.
Detection Guidance
Organizations should monitor for indicators of exploitation, such as abnormal behavior in applications using OpenSSL, unexpected application crashes, or signs of memory corruption. Logging should be configured to capture anomalies related to the use of EVP_PKEY_decrypt() and other cryptographic functions.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2021-3711 lies in its demonstration of the vulnerabilities present in cryptographic implementations. This incident highlights the importance of rigorous testing and validation in cryptographic libraries. Security teams should learn from this vulnerability to bolster their defenses against similar flaws in the future. For further reading on vulnerability management and mitigation strategies, consider reviewing our insights on vulnerability management programs and the latest trends in penetration testing to ensure comprehensive security measures.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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