CVE-2021-44758 : Security Advisory and Response

Heimdal before 7.7.1 allows attackers to cause a NULL pointer dereference in a SPNEGO acceptor via a preferred_mech_type of GSS_C_NO_OID and a nonzero initial_response value to send_accept.

Understanding CVE-2021-44758

This CVE involves a vulnerability in Heimdal, specifically affecting versions prior to 7.7.1.

What is CVE-2021-44758?

CVE-2021-44758 is a security flaw in Heimdal that enables attackers to trigger a NULL pointer dereference within a SPNEGO acceptor. This can be achieved by utilizing a preferred_mech_type of GSS_C_NO_OID and providing a nonzero initial_response value to send_accept.

The Impact of CVE-2021-44758

The exploitation of this vulnerability can lead to a NULL pointer dereference, which may result in a denial of service (DoS) condition or potential arbitrary code execution.

Technical Details of CVE-2021-44758

This section dives into the technical aspects of the CVE.

Vulnerability Description

The issue arises from improper handling of SPNEGO negotiations in Heimdal before version 7.7.1, allowing for a NULL pointer dereference when certain values are provided.

Affected Systems and Versions

Vendor: n/a
Product: n/a
Versions Affected: All versions before 7.7.1

Exploitation Mechanism

Attackers can exploit this vulnerability by manipulating the preferred_mech_type parameter and providing a specific initial_response value, leading to the NULL pointer dereference.

Mitigation and Prevention

Protecting systems from CVE-2021-44758 requires specific actions to mitigate the risk.

Immediate Steps to Take

Update Heimdal to version 7.7.1 or newer to address the vulnerability.
Monitor for any unusual activity related to SPNEGO negotiations.
Implement network-level controls to detect and block potentially malicious requests.

Long-Term Security Practices

Conduct regular security assessments and audits of software components.
Train personnel on secure coding practices and the importance of timely updates.

Patching and Updates

Regularly apply patches and updates provided by Heimdal to ensure that known vulnerabilities are addressed swiftly.