Executive brief
A vulnerability in the Go programming language's standard library can allow an attacker to crash or slow down applications that process digital certificates. This affects services that use Go for secure communications (TLS) or certificate validation, potentially leading to a denial of service. Organizations using Go-based applications should update to the latest patched versions to maintain service availability.
Technical details
A denial of service vulnerability exists in the Go standard library's crypto/x509 package during the certificate chain building process. The root cause is an insufficient limit on the amount of computational work performed when a large number of candidate intermediate certificates are provided in VerifyOptions.Intermediates. An unauthenticated remote attacker can exploit this by providing a specially crafted set of certificates during a TLS handshake or certificate verification call, leading to excessive CPU consumption. This affects both direct users of crypto/x509 and any service using crypto/tls for secure connections. The issue is fixed in Go versions 1.25.9 and 1.26.2.
Affected products
- Google Go before 1.25.9, 1.26.0 before 1.26.2
Timeline
- 2026-03-22: disclosed: Issue reported to Go security team
- 2026-04-07: advisory: Go vulnerability report GO-2026-4947 published
- 2026-04-08: advisory: NVD CVE published
- 2026-04-23: patched: Red Hat security advisory published for RHEL 10