CVE-2018-16875 in Google
Summary
by MITRE
The crypto/x509 package of Go before 1.10.6 and 1.11.x before 1.11.3 does not limit the amount of work performed for each chain verification, which might allow attackers to craft pathological inputs leading to a CPU denial of service. Go TLS servers accepting client certificates and TLS clients are affected.
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Analysis
by VulDB Data Team • 06/19/2023
The vulnerability identified as CVE-2018-16875 represents a critical denial of service weakness within the go programming language's cryptographic x509 package. This flaw affects versions prior to 1.10.6 and 1.11.3, creating a scenario where malicious actors can exploit the certificate chain verification process to consume excessive CPU resources. The vulnerability specifically targets the cryptographic verification mechanisms that occur during TLS handshakes when client certificates are processed, making it particularly dangerous in environments where mutual TLS authentication is employed.
The technical root cause stems from inadequate resource limiting within the certificate chain validation algorithm. When processing certificate chains, the affected go versions perform an unbounded amount of work during verification operations, particularly when encountering pathological certificate structures. This lack of computational bounds allows attackers to craft specially constructed certificate chains that force the verification process to perform exponentially increasing amounts of work. The vulnerability operates at the level of certificate parsing and validation, where each certificate in the chain undergoes extensive cryptographic checks including signature verification, expiration date validation, and chain traversal operations.
The operational impact of this vulnerability extends beyond simple resource exhaustion to potentially disrupt critical services that rely on TLS authentication. Systems running affected go versions become susceptible to CPU-based denial of service attacks where an attacker can send a single malicious client certificate that causes the server to consume excessive processing time. This affects both TLS servers that accept client certificates and TLS clients that validate server certificates, creating a broad attack surface. The vulnerability is particularly concerning in high-traffic environments where a single connection attempt could consume significant computational resources, potentially leading to cascading failures across multiple service instances.
Mitigation strategies for CVE-2018-16875 involve upgrading to patched versions of the go programming language, specifically go 1.10.6 or 1.11.3 and later releases. Organizations should also implement additional protective measures including rate limiting for TLS handshake operations, connection pooling optimizations, and monitoring for unusual CPU consumption patterns during certificate validation. The vulnerability aligns with CWE-770, which describes allocation of resources without limits or throttling, and can be categorized under ATT&CK technique T1499.001 for resource exhaustion attacks. Network administrators should also consider implementing certificate validation timeouts and limiting the maximum depth of certificate chains to prevent exploitation of this vulnerability in environments where immediate upgrades are not feasible.