CVE-2018-0739 : Exploit Details and Defense Strategies

CVE-2018-0739, also known as 'Constructed ASN.1 types with a recursive definition could exceed the stack,' is a vulnerability in OpenSSL that could lead to a Denial of Service attack.

Understanding CVE-2018-0739

This CVE entry addresses a specific vulnerability in OpenSSL related to ASN.1 types with recursive definitions.

What is CVE-2018-0739?

ASN.1 types with recursive definitions, such as those found in PKCS7, could potentially exceed the stack limit when subjected to malicious input with excessive recursion. While this could result in a Denial of Service attack, it's important to note that SSL/TLS does not use such structures from untrusted sources, ensuring safety.

The Impact of CVE-2018-0739

The vulnerability could be exploited to cause a Denial of Service attack by exceeding the stack limit with malicious input. However, SSL/TLS implementations are not affected as they do not utilize these structures from untrusted sources.

Technical Details of CVE-2018-0739

This section provides more in-depth technical details about the vulnerability.

Vulnerability Description

Constructed ASN.1 types with recursive definitions, like those in PKCS7, could exceed the stack limit when exposed to malicious input with excessive recursion, potentially leading to a Denial of Service attack.

Affected Systems and Versions

OpenSSL 1.1.0h (Affected versions: 1.1.0-1.1.0g)
OpenSSL 1.0.2o (Affected versions: 1.0.2b-1.0.2n)

Exploitation Mechanism

The vulnerability can be exploited by providing malicious input with excessive recursion to ASN.1 types with recursive definitions, causing the stack to be exceeded and potentially leading to a Denial of Service attack.

Mitigation and Prevention

Protecting systems from CVE-2018-0739 involves taking immediate steps and implementing long-term security practices.

Immediate Steps to Take

Apply the necessary patches provided by OpenSSL to address the vulnerability.
Monitor for any unusual activity that could indicate exploitation of the vulnerability.

Long-Term Security Practices

Regularly update OpenSSL to the latest versions to ensure that known vulnerabilities are patched.
Implement secure coding practices to prevent similar vulnerabilities in the future.

Patching and Updates

Ensure that all affected systems are updated with the fixed versions of OpenSSL (1.1.0h and 1.0.2o) to mitigate the CVE-2018-0739 vulnerability.