CVE-2016-7141 in macOS
Summary
by MITRE
curl and libcurl before 7.50.2, when built with NSS and the libnsspem.so library is available at runtime, allow remote attackers to hijack the authentication of a TLS connection by leveraging reuse of a previously loaded client certificate from file for a connection for which no certificate has been set, a different vulnerability than CVE-2016-5420.
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Analysis
by VulDB Data Team • 10/07/2022
The vulnerability identified as CVE-2016-7141 affects curl and libcurl versions prior to 7.50.2 when configured with Network Security Services NSS and the libnsspem.so library is present at runtime. This represents a significant security flaw in the handling of TLS client certificate authentication within the curl library ecosystem. The issue stems from improper certificate management during connection reuse scenarios, creating a potential avenue for man-in-the-middle attacks and unauthorized authentication manipulation.
The technical flaw manifests when curl reuses a previously loaded client certificate from a file for subsequent connections, even when no specific certificate has been explicitly configured for the current connection attempt. This behavior occurs specifically within NSS-enabled builds where the libnsspem.so library is available and active. The vulnerability allows remote attackers to exploit the certificate reuse mechanism by manipulating the connection state to leverage an already-loaded certificate, effectively bypassing proper authentication controls that should be enforced for each individual connection attempt.
From an operational impact perspective, this vulnerability creates a serious risk for applications that rely on curl for secure HTTP communications with client certificate authentication. Attackers could potentially intercept and manipulate TLS connections without proper authorization, especially in environments where multiple connections are made using the same curl instance. The vulnerability is particularly concerning because it operates silently in the background, allowing unauthorized certificate reuse without explicit user configuration or awareness. This issue differs from CVE-2016-5420, which addressed a different aspect of certificate handling, making CVE-2016-7141 a distinct but equally serious concern in the TLS certificate management space.
The vulnerability aligns with CWE-310, which addresses cryptographic issues related to improper certificate handling and authentication mechanisms. From an ATT&CK framework perspective, this vulnerability maps to T1566, specifically targeting credential access through manipulation of authentication mechanisms, and potentially T1046, as it could enable network infiltration through compromised TLS connections. Organizations using curl or libcurl with NSS support should prioritize immediate patching to address this vulnerability, as it represents a fundamental flaw in how client certificate authentication is managed during connection reuse scenarios, potentially allowing attackers to impersonate legitimate users or systems within secure communication channels.
The root cause of this vulnerability lies in the improper state management of client certificate objects within the NSS integration layer of curl. When the libnsspem.so library is available, the system maintains certificate state between connections without proper validation of whether the certificate should be reused for the current connection context. This design flaw creates an authentication bypass opportunity where attackers can manipulate connection parameters to leverage previously loaded certificates, effectively undermining the security controls that should govern each individual TLS connection establishment. The vulnerability demonstrates the importance of proper certificate lifecycle management and the dangers of implicit certificate reuse in security-sensitive applications.