Executive Summary

This vulnerability involves wget2 accepting a server certificate that has incorrect Key Usage (KU) or Extended Key Usage (EKU) attributes. Normally, certificates are issued for specific purposes, and these attributes define what the certificate can be used for. However, due to this flaw, if an attacker compromises a certificate (including its private key) that was issued for a different purpose, they might be able to reuse it to authenticate a TLS server.

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Impact Analysis

If exploited, this vulnerability could allow an attacker to impersonate a legitimate TLS server by reusing a compromised certificate that was not originally intended for server authentication. This could lead to man-in-the-middle attacks, where the attacker intercepts or alters communications between a user and a server, potentially exposing sensitive information or enabling further attacks.

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Executive Summary

This vulnerability in wget2 involves improper validation of server certificates. Specifically, wget2 accepts server certificates that have incorrect Key Usage (KU) or Extended Key Usage (EKU) extensions.

Attackers who manage to compromise a certificate (and its private key) that was originally issued for a different purpose could exploit this flaw by reusing that certificate for TLS server authentication, which wget2 should not allow.

A Proof of Concept demonstrated that wget2 fails to properly validate whether a certificate is intended for TLS server authentication, even if the KU or EKU settings are incorrect.

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Impact Analysis

This vulnerability can allow attackers to impersonate a legitimate TLS server by using a compromised certificate that was not meant for server authentication.

As a result, users of wget2 could be tricked into establishing secure connections with malicious servers, potentially leading to interception or manipulation of sensitive data.

The impact includes limited confidentiality and integrity risks, as indicated by the CVSS score, but no impact on availability.

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Detection Guidance

This vulnerability involves wget2 accepting server certificates with incorrect Key Usage (KU) or Extended Key Usage (EKU). Detection would involve verifying whether wget2 is validating server certificates properly during TLS connections.

A practical approach to detect this vulnerability is to test wget2 connections against a server presenting a certificate with incorrect KU or EKU extensions. If wget2 accepts such a certificate without error, the vulnerability is present.

Since the vulnerability is specific to wget2, you can check the version of wget2 installed using the command:

• wget2 --version

Versions prior to v2.2.2 are vulnerable. To test certificate validation behavior, you could use wget2 to connect to a test server configured with a certificate having incorrect KU or EKU. However, no specific detection commands are provided in the available resources.

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Mitigation Strategies

The immediate mitigation step is to upgrade wget2 to version 2.2.2 or later, where the vulnerability has been fixed.

Avoid using vulnerable versions of wget2 to connect to untrusted servers, especially those that might present certificates with incorrect Key Usage or Extended Key Usage.

Coordinate with your security team to ensure that any automated systems or scripts using wget2 are updated promptly to the fixed version.

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Compliance Impact

The provided information does not specify how this vulnerability affects compliance with common standards and regulations such as GDPR or HIPAA.

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