src/crypto/x509/name_constraints_test.go | 17 +++++++++++++++++
 src/crypto/x509/verify.go                |  7 +++++--

diff --git a/src/crypto/x509/name_constraints_test.go b/src/crypto/x509/name_constraints_test.go
index 008c7028f4e4c44acc8dd3d6afa5b43dad736d7e..a5851845164d1021f417e937d08aef9e943fa346 100644
--- a/src/crypto/x509/name_constraints_test.go
+++ b/src/crypto/x509/name_constraints_test.go
@@ -1607,6 +1607,23 @@ 		roots:         []constraintsSpec{{ok: []string{"dns:example.com"}}},
 		leaf:          leafSpec{sans: []string{"dns:.example.com"}},
 		expectedError: "cannot parse dnsName \".example.com\"",
 	},
+	// #86: URIs with IPv6 addresses with zones and ports are rejected
+	{
+		roots: []constraintsSpec{
+			{
+				ok: []string{"uri:example.com"},
+			},
+		},
+		intermediates: [][]constraintsSpec{
+			{
+				{},
+			},
+		},
+		leaf: leafSpec{
+			sans: []string{"uri:http://[2006:abcd::1%25.example.com]:16/"},
+		},
+		expectedError: "URI with IP",
+	},
 }
 
 func makeConstraintsCACert(constraints constraintsSpec, name string, key *ecdsa.PrivateKey, parent *Certificate, parentKey *ecdsa.PrivateKey) (*Certificate, error) {
diff --git a/src/crypto/x509/verify.go b/src/crypto/x509/verify.go
index 7170087287644e76f9180993637d855fcce74d84..bbccfce57742c018a7bcde27b2a198b0ff2df787 100644
--- a/src/crypto/x509/verify.go
+++ b/src/crypto/x509/verify.go
@@ -11,6 +11,7 @@ 	"crypto/x509/pkix"
 	"errors"
 	"fmt"
 	"net"
+	"net/netip"
 	"net/url"
 	"reflect"
 	"runtime"
@@ -434,8 +435,10 @@ 			return false, err
 		}
 	}
 
-	if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") ||
-		net.ParseIP(host) != nil {
+	// netip.ParseAddr will reject the URI IPv6 literal form "[...]", so we
+	// check if _either_ the string parses as an IP, or if it is enclosed in
+	// square brackets.
+	if _, err := netip.ParseAddr(host); err == nil || (strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]")) {
 		return false, fmt.Errorf("URI with IP (%q) cannot be matched against constraints", uri.String())
 	}