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CVE PROGRAM SOURCE RECORD6.5 Medium

CVE-2026-27145

Inefficient candidate hostname parsing in crypto/x509

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Status
Published
Published
Updated
Assigning organization
Go

Description

(*x509.Certificate).VerifyHostname previously called matchHostnames in a loop over all DNS Subject Alternative Name (SAN) entries. This caused strings.Split(host, ".") to execute repeatedly on the same input hostname. With a large DNS SAN list, verification costs scaled quadratically based on the number of SAN entries multiplied by the hostname's label count. Because x509.Verify validates hostnames before building the certificate chain, this overhead occurred even for untrusted certificates.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Go standard library crypto/x509

Default version status: unaffected

  • 0 to < 1.25.11affected
  • 1.26.0-0 to < 1.26.4affected

References