CVE-2021-44532 in Node.js
Summary
by MITRE • 02/24/2022
Node.js < 12.22.9, < 14.18.3, < 16.13.2, and < 17.3.1 converts SANs (Subject Alternative Names) to a string format. It uses this string to check peer certificates against hostnames when validating connections. The string format was subject to an injection vulnerability when name constraints were used within a certificate chain, allowing the bypass of these name constraints.Versions of Node.js with the fix for this escape SANs containing the problematic characters in order to prevent the injection. This behavior can be reverted through the --security-revert command-line option.
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Analysis
by VulDB Data Team • 12/12/2024
The vulnerability described in CVE-2021-44532 represents a critical security flaw in Node.js certificate validation mechanisms that directly impacts the integrity of secure communications. This issue affects multiple Node.js version lines including the 12.x, 14.x, 16.x, and 17.x branches, with specific patched versions outlined in the advisory. The vulnerability stems from how Node.js processes Subject Alternative Names within X.509 certificates during SSL/TLS connection validation, creating a potential attack vector that could allow malicious actors to bypass certificate validation controls.
The technical root cause of this vulnerability lies in the conversion process of SANs to string format for hostname validation purposes. When certificates contain name constraints within their chains, the string representation used by Node.js for comparison becomes susceptible to injection attacks. This flaw specifically manifests when SANs contain problematic characters that can manipulate the string parsing logic, allowing attackers to craft certificates that appear valid but actually bypass the intended name constraint enforcement. The vulnerability operates at the level of certificate chain validation and can be categorized under CWE-22 as "Improper Limitation of a Pathname to a Restricted Directory" and CWE-770 as "Allocation of Resources Without Limits or Throttling" in the context of certificate validation.
The operational impact of CVE-2021-44532 extends beyond simple certificate validation bypasses, potentially enabling man-in-the-middle attacks where malicious certificates can successfully validate against target hostnames. Attackers can exploit this vulnerability to create certificate chains that circumvent the name constraint checks, effectively allowing them to impersonate legitimate services within the same domain or subdomain structure. This vulnerability particularly affects applications that rely on strict certificate validation for security, including web servers, API gateways, and any service that performs SSL/TLS certificate verification. The attack vector operates through the certificate validation process defined in the Transport Layer Security protocol, specifically targeting the hostname verification mechanism that is fundamental to secure communication channels.
The Node.js development team addressed this vulnerability by implementing proper escaping mechanisms for SANs containing problematic characters, ensuring that name constraints within certificate chains are properly enforced. This fix prevents the injection attack by sanitizing the string representations before hostname validation occurs. Organizations can also utilize the --security-revert command-line option to restore the previous behavior, though this is strongly discouraged in production environments. The mitigation strategy aligns with ATT&CK technique T1552.001 as "Credentials in Files" and T1071.001 as "Application Layer Protocol: Web Protocols", since the vulnerability specifically impacts the secure handling of certificate credentials during web communication. System administrators should prioritize updating affected Node.js installations to the patched versions, as the vulnerability can be exploited to establish unauthorized secure connections that would otherwise be blocked by proper certificate validation. The security implications extend to any application stack that depends on Node.js for secure communications, making this vulnerability particularly dangerous in enterprise environments where certificate validation serves as a critical security control.