CVE-2020-28481 in socket.io Packet
Summary
by MITRE • 01/19/2021
The package socket.io before 2.4.0 are vulnerable to Insecure Defaults due to CORS Misconfiguration. All domains are whitelisted by default.
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Analysis
by VulDB Data Team • 02/15/2021
The vulnerability identified as CVE-2020-28481 affects the socket.io package versions prior to 2.4.0, representing a critical security flaw stemming from insecure default configurations. This issue manifests through a cross-origin resource sharing cors misconfiguration that fundamentally undermines the security posture of applications relying on this websocket library. The vulnerability arises from the package's default behavior of whitelisting all domains, which creates an expansive attack surface that malicious actors can exploit to bypass intended security boundaries.
The technical flaw resides in the default cors configuration settings within socket.io's implementation where no restrictions are applied to origin validation by default. This insecure default means that any domain can establish connections to websocket endpoints without proper authentication or authorization checks, effectively disabling the cors protection mechanism that should normally prevent unauthorized cross-origin requests. The vulnerability specifically impacts the websocket communication layer and can be categorized under the CWE-693 weakness pattern related to protection mechanism failures, where the intended security controls are either absent or misconfigured.
The operational impact of this vulnerability extends beyond simple data exposure to encompass potential complete system compromise. Attackers can leverage this misconfiguration to perform cross-site request forgery attacks, hijack websocket connections, or inject malicious data into communication channels. Applications using affected versions of socket.io become vulnerable to man-in-the-middle attacks where unauthorized domains can establish persistent connections and potentially access sensitive data streams. This vulnerability directly relates to the ATT&CK technique T1071.004 for application layer protocol and T1566 for credential access through social engineering, as the insecure defaults can facilitate unauthorized access to websocket endpoints.
Organizations implementing socket.io in their applications face significant risk exposure due to this vulnerability, particularly in environments where sensitive data is transmitted through websocket connections. The default whitelisting behavior means that even in production environments where proper security configurations should be implemented, applications may remain vulnerable if developers rely on default settings without proper validation. This issue is particularly concerning in multi-tenant environments or applications handling personal identifiable information, where unauthorized cross-origin access could lead to data breaches and compliance violations.
The recommended mitigation strategy involves upgrading to socket.io version 2.4.0 or later, which addresses the cors misconfiguration by implementing proper default restrictions. Security teams should also conduct comprehensive audits of their websocket implementations to ensure that cors policies are properly configured with explicit origin whitelisting rather than relying on default insecure settings. Additional protective measures include implementing proper authentication mechanisms for websocket connections, monitoring websocket traffic for unauthorized access attempts, and regularly reviewing cors configurations to prevent similar vulnerabilities in other components of the application stack. The fix addresses the core issue by enforcing strict origin validation and removing the default permissive behavior that enabled unauthorized access to websocket endpoints.