A weakness in the Go standard library crypto/x509 package allows an attacker to cause excessive CPU and memory usage during certificate chain verification. When a very large list of intermediate certificates is supplied to VerifyOptions.Intermediates, the routine performs more work than intended, potentially hanging or crashing the verifier. The flaw is classified as a resource exhaustion vulnerability (CWE‑770).

All Go programs that use the standard library’s X509 verification logic are affected, including direct users of crypto/x509 and any components that depend on it such as crypto/tls.

The CVSS score of 7.5 marks the issue as high severity, while the EPSS score of less than 1 % indicates a low likelihood of exploitation. The flaw is not listed in the CISA Known Exploited Vulnerabilities catalog. An adversary can trigger the denial of service by delivering a crafted chain of many intermediate certificates during a TLS handshake or by directly invoking the verification function from application code. The impact is limited to availability, but it can disrupt services that perform certificate validation.