Vulnerability DatabaseCVE-2021-23365

CVE-2021-23365:
vulnerability analysis and mitigation

Overview

CVE-2021-23365 is a vulnerability in the Go XML parser affecting SAML authentication in Tyk Identity Broker versions prior to 1.1.1. The vulnerability was disclosed on March 30, 2021, and published on April 22, 2021. The issue stems from the XML parser's inability to guarantee integrity during XML round-trip operations (encoding/decoding XML data), which could potentially lead to SAML authentication bypass (Snyk, GitHub Release).

Technical details

The vulnerability exists in the SAML implementation where the Go XML parser's handling of XML round-trip operations could be exploited. The issue received a CVSS v3.1 base score of 4.8 (medium) according to Snyk's assessment, with Network attack vector, High attack complexity, and No privileges required. The vulnerability is tracked as CWE-287, related to improper authentication (Snyk).

Impact

If exploited, this vulnerability could allow an attacker to bypass SAML authentication mechanisms. The impact includes potential unauthorized access to protected resources, with some loss of confidentiality and integrity, though the attacker's control over the extent of the impact is limited (Snyk).

Exploitability

The vulnerability requires network access and has high attack complexity, meaning successful exploitation cannot be accomplished at will but requires significant preparation. No user interaction is required for exploitation, and the attacker doesn't need prior privileges (Snyk).

Mitigation and workarounds

The vulnerability was fixed in Tyk Identity Broker version 1.1.1. Users are advised to upgrade to this version or higher. The fix involved integrating github.com/mattermost/xml-roundtrip-validator into the SAML project, as there was no native fix available in the Go language at the time (GitHub PR, GitHub Release).

Community reactions

The Go security team acknowledged the issue but chose not to implement a fix in the core language, stating that round-trip stability was not a currently supported security property of encoding/xml. They determined that the encoding/xml package and its data structures were not designed to make safe round-trips possible (GitHub PR).