CVE-2021-3449 : Exploit Details and Defense Strategies
Understand CVE-2021-3449, a vulnerability in OpenSSL that allows a denial of service attack. Learn about impacted systems, mitigation steps, and prevention measures.
This article provides detailed information about CVE-2021-3449, a vulnerability in OpenSSL that could lead to a denial of service attack.
Understanding CVE-2021-3449
CVE-2021-3449 is a NULL pointer dereference vulnerability in OpenSSL that can cause a server to crash when sent a maliciously crafted renegotiation ClientHello message.
What is CVE-2021-3449?
An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello omits the signature_algorithms extension but includes a signature_algorithms_cert extension, a NULL pointer dereference will occur, leading to a crash and a denial of service attack.
The Impact of CVE-2021-3449
Servers with TLSv1.2 and renegotiation enabled are vulnerable. All OpenSSL 1.1.1 versions are affected by this issue. Users should upgrade to OpenSSL 1.1.1k to mitigate the vulnerability. OpenSSL 1.0.2 is not impacted.
Technical Details of CVE-2021-3449
This section details the vulnerability description, affected systems, and the exploitation mechanism.
Vulnerability Description
The vulnerability arises from a NULL pointer dereference in signature_algorithms processing in OpenSSL.
Affected Systems and Versions
OpenSSL 1.1.1 versions are affected, while OpenSSL 1.0.2 is not vulnerable to this issue.
Exploitation Mechanism
Exploiting this vulnerability requires sending a crafted renegotiation ClientHello message to an OpenSSL TLS server.
Mitigation and Prevention
Learn how to mitigate the impact of CVE-2021-3449 and prevent similar vulnerabilities.
Immediate Steps to Take
Update to OpenSSL 1.1.1k to address the vulnerability and prevent crashes on vulnerable servers.
Long-Term Security Practices
Secure your systems by following best security practices, including regular updates and secure configurations.
Patching and Updates
Stay informed about security patches and updates provided by OpenSSL to protect your systems from known vulnerabilities.