CVE-2018-16253 : Security Advisory and Response

CVE-2018-16253 was published on October 22, 2018, and affects axTLS versions 2.1.3 and earlier. The vulnerability lies in the incorrect verification of ASN.1 metadata during PKCS#1 v1.5 signature verification in the sig_verify() function of x509.c.

Understanding CVE-2018-16253

This CVE highlights a flaw in the signature verification process that can be exploited by remote attackers to create forged signatures, potentially leading to impersonation through the use of fraudulent X.509 certificates.

What is CVE-2018-16253?

The vulnerability in sig_verify() function of x509.c in axTLS versions 2.1.3 and earlier allows remote attackers to forge signatures when small public exponents are used, enabling impersonation through fake X.509 certificates. It is a more lenient variant of CVE-2006-4790 and CVE-2014-1568.

The Impact of CVE-2018-16253

The vulnerability poses a significant risk of impersonation and fraudulent activities due to the creation of forged signatures by remote attackers.

Technical Details of CVE-2018-16253

The technical details of this CVE are as follows:

Vulnerability Description

The PKCS#1 v1.5 signature verification in sig_verify() function of x509.c in axTLS versions 2.1.3 and earlier does not correctly verify the ASN.1 metadata, allowing for the creation of forged signatures.

Affected Systems and Versions

Product: n/a
Vendor: n/a
Versions affected: All versions prior to 2.1.3

Exploitation Mechanism

The vulnerability can be exploited remotely by utilizing small public exponents to create forged signatures, enabling impersonation through fraudulent X.509 certificates.

Mitigation and Prevention

To address CVE-2018-16253, the following steps can be taken:

Immediate Steps to Take

Update axTLS to version 2.1.4 or later to mitigate the vulnerability.
Monitor for any suspicious activities related to signature verification.

Long-Term Security Practices

Regularly review and update cryptographic libraries to ensure they are secure.
Implement strong certificate validation practices to prevent the use of fraudulent certificates.

Patching and Updates

Apply patches and updates provided by axTLS promptly to address security vulnerabilities and enhance system security.