diff --git a/custom/conf/app.example.ini b/custom/conf/app.example.ini
index 9297f3d062721..0a3f4b3b5b10e 100644
--- a/custom/conf/app.example.ini
+++ b/custom/conf/app.example.ini
@@ -1648,23 +1648,24 @@ LEVEL = Info
 ;;  - <username>.livejournal.com
 ;;
 ;; Whether to allow signin in via OpenID
-;ENABLE_OPENID_SIGNIN = true
+;ENABLE_OPENID_SIGNIN = false
 ;;
 ;; Whether to allow registering via OpenID
 ;; Do not include to rely on rhw DISABLE_REGISTRATION setting
 ;;ENABLE_OPENID_SIGNUP = true
 ;;
-;; Allowed URI patterns (POSIX regexp).
-;; Space separated.
-;; Only these would be allowed if non-blank.
-;; Example value: trusted.domain.org trusted.domain.net
+;; Allowed OpenID provider hosts (host matcher).
+;; Space or comma separated.
+;; Only these would be allowed if non-blank. Matches the host portion only.
+;; Example value: trusted.domain.org *.trusted.domain.net
 ;WHITELISTED_URIS =
 ;;
-;; Forbidden URI patterns (POSIX regexp).
-;; Space separated.
+;; Blocked OpenID provider hosts (host matcher).
+;; Space or comma separated.
 ;; Only used if WHITELISTED_URIS is blank.
-;; Example value: loadaverage.org/badguy stackexchange.com/.*spammer
-;BLACKLISTED_URIS =
+;; Built-in: loopback (localhost), private (LAN/intranet), external (public hosts), * (all hosts)
+;; Default value blocks localhost, loopback, private, and IPv6 link-local to avoid SSRF.
+;BLACKLISTED_URIS = localhost loopback private 169.254.0.0/16 fe80::/10
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
diff --git a/modules/setting/openid.go b/modules/setting/openid.go
new file mode 100644
index 0000000000000..04f8c55f67761
--- /dev/null
+++ b/modules/setting/openid.go
@@ -0,0 +1,63 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"strings"
+
+	"code.gitea.io/gitea/modules/hostmatcher"
+)
+
+// OpenID settings
+var OpenID = struct {
+	EnableSignIn bool
+	EnableSignUp bool
+	Allowlist    *hostmatcher.HostMatchList
+	Blocklist    *hostmatcher.HostMatchList
+}{
+	EnableSignIn: false,
+	EnableSignUp: false,
+	Allowlist:    nil,
+	Blocklist:    nil,
+}
+
+var defaultOpenIDBlocklist = []string{
+	"localhost",
+	hostmatcher.MatchBuiltinLoopback,
+	hostmatcher.MatchBuiltinPrivate,
+	"169.254.0.0/16",
+	"fe80::/10",
+}
+
+func splitOpenIDHostList(raw string) []string {
+	return strings.FieldsFunc(raw, func(r rune) bool {
+		switch r {
+		case ',', ' ', '\t', '\n', '\r':
+			return true
+		default:
+			return false
+		}
+	})
+}
+
+// loadOpenIDSetting loads OpenID settings from rootCfg, depends on service settings,
+// so should be called after loadServiceSettings.
+func loadOpenIDSetting(rootCfg ConfigProvider) {
+	sec := rootCfg.Section("openid")
+	OpenID.EnableSignIn = sec.Key("ENABLE_OPENID_SIGNIN").MustBool(false)
+	OpenID.EnableSignUp = sec.Key("ENABLE_OPENID_SIGNUP").MustBool(!Service.DisableRegistration && OpenID.EnableSignIn)
+	OpenID.Allowlist = nil
+	OpenID.Blocklist = nil
+	allowlist := splitOpenIDHostList(sec.Key("WHITELISTED_URIS").String())
+	if len(allowlist) != 0 {
+		OpenID.Allowlist = hostmatcher.ParseHostMatchList("openid.WHITELISTED_URIS", strings.Join(allowlist, ","))
+	}
+	blocklist := splitOpenIDHostList(sec.Key("BLACKLISTED_URIS").String())
+	if len(blocklist) == 0 {
+		blocklist = defaultOpenIDBlocklist
+	}
+	if len(blocklist) != 0 {
+		OpenID.Blocklist = hostmatcher.ParseHostMatchList("openid.BLACKLISTED_URIS", strings.Join(blocklist, ","))
+	}
+}
diff --git a/modules/setting/openid_test.go b/modules/setting/openid_test.go
new file mode 100644
index 0000000000000..7708412aabee5
--- /dev/null
+++ b/modules/setting/openid_test.go
@@ -0,0 +1,73 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/modules/test"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestLoadOpenIDSettings(t *testing.T) {
+	defer test.MockVariableValue(&Service)()
+
+	t.Run("DefaultBlacklist", func(t *testing.T) {
+		cfg, err := NewConfigProviderFromData(`
+[openid]
+`)
+		assert.NoError(t, err)
+		loadServiceFrom(cfg)
+
+		assert.False(t, OpenID.EnableSignIn)
+		assert.False(t, OpenID.EnableSignUp)
+		assert.Nil(t, OpenID.Allowlist)
+		if assert.NotNil(t, OpenID.Blocklist) {
+			assert.True(t, OpenID.Blocklist.MatchHostName("localhost"))
+			assert.True(t, OpenID.Blocklist.MatchHostName("127.0.0.1"))
+			assert.True(t, OpenID.Blocklist.MatchHostName("192.168.0.1"))
+			assert.True(t, OpenID.Blocklist.MatchHostName("fe80::1"))
+			assert.False(t, OpenID.Blocklist.MatchHostName("example.com"))
+		}
+	})
+
+	t.Run("AllowlistParsing", func(t *testing.T) {
+		cfg, err := NewConfigProviderFromData(`
+[openid]
+ENABLE_OPENID_SIGNIN = true
+WHITELISTED_URIS = example.com, *.trusted.example
+`)
+		assert.NoError(t, err)
+		loadServiceFrom(cfg)
+
+		assert.True(t, OpenID.EnableSignIn)
+		assert.True(t, OpenID.EnableSignUp)
+		if assert.NotNil(t, OpenID.Allowlist) {
+			assert.True(t, OpenID.Allowlist.MatchHostName("example.com"))
+			assert.True(t, OpenID.Allowlist.MatchHostName("foo.trusted.example"))
+			assert.False(t, OpenID.Allowlist.MatchHostName("example.org"))
+		}
+		if assert.NotNil(t, OpenID.Blocklist) {
+			assert.True(t, OpenID.Blocklist.MatchHostName("localhost"))
+		}
+	})
+
+	t.Run("BlocklistParsing", func(t *testing.T) {
+		cfg, err := NewConfigProviderFromData(`
+[openid]
+BLACKLISTED_URIS = bad.example.com, 10.0.0.0/8
+`)
+		assert.NoError(t, err)
+		loadServiceFrom(cfg)
+
+		assert.Nil(t, OpenID.Allowlist)
+		if assert.NotNil(t, OpenID.Blocklist) {
+			assert.True(t, OpenID.Blocklist.MatchHostName("bad.example.com"))
+			assert.True(t, OpenID.Blocklist.MatchHostName("10.1.1.1"))
+			assert.False(t, OpenID.Blocklist.MatchHostName("localhost"))
+			assert.False(t, OpenID.Blocklist.MatchHostName("good.example.com"))
+		}
+	})
+}
diff --git a/modules/setting/service.go b/modules/setting/service.go
index e652c13c9c9e3..1f5e00463c4a5 100644
--- a/modules/setting/service.go
+++ b/modules/setting/service.go
@@ -4,7 +4,6 @@
 package setting
 
 import (
-	"regexp"
 	"runtime"
 	"strings"
 	"time"
@@ -85,12 +84,6 @@ var Service = struct {
 	UserDeleteWithCommentsMaxTime           time.Duration
 	ValidSiteURLSchemes                     []string
 
-	// OpenID settings
-	EnableOpenIDSignIn bool
-	EnableOpenIDSignUp bool
-	OpenIDWhitelist    []*regexp.Regexp
-	OpenIDBlacklist    []*regexp.Regexp
-
 	// Explore page settings
 	Explore struct {
 		RequireSigninView        bool `ini:"REQUIRE_SIGNIN_VIEW"`
@@ -265,26 +258,6 @@ func loadServiceFrom(rootCfg ConfigProvider) {
 	loadQosSetting(rootCfg)
 }
 
-func loadOpenIDSetting(rootCfg ConfigProvider) {
-	sec := rootCfg.Section("openid")
-	Service.EnableOpenIDSignIn = sec.Key("ENABLE_OPENID_SIGNIN").MustBool(!InstallLock)
-	Service.EnableOpenIDSignUp = sec.Key("ENABLE_OPENID_SIGNUP").MustBool(!Service.DisableRegistration && Service.EnableOpenIDSignIn)
-	pats := sec.Key("WHITELISTED_URIS").Strings(" ")
-	if len(pats) != 0 {
-		Service.OpenIDWhitelist = make([]*regexp.Regexp, len(pats))
-		for i, p := range pats {
-			Service.OpenIDWhitelist[i] = regexp.MustCompilePOSIX(p)
-		}
-	}
-	pats = sec.Key("BLACKLISTED_URIS").Strings(" ")
-	if len(pats) != 0 {
-		Service.OpenIDBlacklist = make([]*regexp.Regexp, len(pats))
-		for i, p := range pats {
-			Service.OpenIDBlacklist[i] = regexp.MustCompilePOSIX(p)
-		}
-	}
-}
-
 func loadQosSetting(rootCfg ConfigProvider) {
 	sec := rootCfg.Section("qos")
 	Service.QoS.Enabled = sec.Key("ENABLED").MustBool(false)
diff --git a/modules/web/middleware/data.go b/modules/web/middleware/data.go
index 41fb1e7e6f64d..6f679e6acd265 100644
--- a/modules/web/middleware/data.go
+++ b/modules/web/middleware/data.go
@@ -32,7 +32,7 @@ func CommonTemplateContextData() reqctx.ContextData {
 		"DisableDownloadSourceArchives": setting.Repository.DisableDownloadSourceArchives,
 
 		"EnableSwagger":      setting.API.EnableSwagger,
-		"EnableOpenIDSignIn": setting.Service.EnableOpenIDSignIn,
+		"EnableOpenIDSignIn": setting.OpenID.EnableSignIn,
 		"PageStartTime":      time.Now(),
 
 		"RunModeIsProd": setting.IsProd,
diff --git a/routers/install/install.go b/routers/install/install.go
index 81fcdfa384c58..42d3fcdf14b5c 100644
--- a/routers/install/install.go
+++ b/routers/install/install.go
@@ -113,8 +113,8 @@ func Install(ctx *context.Context) {
 	form.RegisterConfirm = setting.Service.RegisterEmailConfirm
 	form.MailNotify = setting.Service.EnableNotifyMail
 
-	form.EnableOpenIDSignIn = setting.Service.EnableOpenIDSignIn
-	form.EnableOpenIDSignUp = setting.Service.EnableOpenIDSignUp
+	form.EnableOpenIDSignIn = setting.OpenID.EnableSignIn
+	form.EnableOpenIDSignUp = setting.OpenID.EnableSignUp
 	form.DisableRegistration = setting.Service.DisableRegistration
 	form.AllowOnlyExternalRegistration = setting.Service.AllowOnlyExternalRegistration
 	form.EnableCaptcha = setting.Service.EnableCaptcha
diff --git a/routers/web/admin/config.go b/routers/web/admin/config.go
index a449796ec1295..ff8cc168a5fc3 100644
--- a/routers/web/admin/config.go
+++ b/routers/web/admin/config.go
@@ -142,6 +142,7 @@ func Config(ctx *context.Context) {
 	ctx.Data["LFS"] = setting.LFS
 
 	ctx.Data["Service"] = setting.Service
+	ctx.Data["OpenID"] = setting.OpenID
 	ctx.Data["DbCfg"] = setting.Database
 	ctx.Data["Webhook"] = setting.Webhook
 	ctx.Data["MailerEnabled"] = false
diff --git a/routers/web/auth/openid.go b/routers/web/auth/openid.go
index c9843146d455e..7c5fe3051337c 100644
--- a/routers/web/auth/openid.go
+++ b/routers/web/auth/openid.go
@@ -44,25 +44,30 @@ func SignInOpenID(ctx *context.Context) {
 	ctx.HTML(http.StatusOK, tplSignInOpenID)
 }
 
-// Check if the given OpenID URI is allowed by blacklist/whitelist
+// Check if the given OpenID URI is allowed by blocklist/allowlist
 func allowedOpenIDURI(uri string) (err error) {
+	parsed, err := url.Parse(uri)
+	if err != nil {
+		return err
+	}
+	host := parsed.Hostname()
+	if host == "" {
+		return errors.New("invalid OpenID URI host")
+	}
+
 	// In case a Whitelist is present, URI must be in it
 	// in order to be accepted
-	if len(setting.Service.OpenIDWhitelist) != 0 {
-		for _, pat := range setting.Service.OpenIDWhitelist {
-			if pat.MatchString(uri) {
-				return nil // pass
-			}
+	if allowList := setting.OpenID.Allowlist; allowList != nil && !allowList.IsEmpty() {
+		if allowList.MatchHostName(host) {
+			return nil // pass
 		}
 		// must match one of this or be refused
-		return errors.New("URI not allowed by whitelist")
+		return errors.New("URI not allowed by allowlist")
 	}
 
-	// A blacklist match expliclty forbids
-	for _, pat := range setting.Service.OpenIDBlacklist {
-		if pat.MatchString(uri) {
-			return errors.New("URI forbidden by blacklist")
-		}
+	// A blocklist match expliclty forbids
+	if blockList := setting.OpenID.Blocklist; blockList != nil && blockList.MatchHostName(host) {
+		return errors.New("URI forbidden by blocklist")
 	}
 
 	return nil
@@ -222,7 +227,7 @@ func signInOpenIDVerify(ctx *context.Context) {
 		return
 	}
 
-	if u != nil || !setting.Service.EnableOpenIDSignUp || setting.Service.AllowOnlyInternalRegistration {
+	if u != nil || !setting.OpenID.EnableSignUp || setting.Service.AllowOnlyInternalRegistration {
 		ctx.Redirect(setting.AppSubURL + "/user/openid/connect")
 	} else {
 		ctx.Redirect(setting.AppSubURL + "/user/openid/register")
@@ -239,7 +244,7 @@ func ConnectOpenID(ctx *context.Context) {
 	ctx.Data["Title"] = "OpenID connect"
 	ctx.Data["PageIsSignIn"] = true
 	ctx.Data["PageIsOpenIDConnect"] = true
-	ctx.Data["EnableOpenIDSignUp"] = setting.Service.EnableOpenIDSignUp
+	ctx.Data["EnableOpenIDSignUp"] = setting.OpenID.EnableSignUp
 	ctx.Data["AllowOnlyInternalRegistration"] = setting.Service.AllowOnlyInternalRegistration
 	ctx.Data["OpenID"] = oid
 	userName, _ := ctx.Session.Get("openid_determined_username").(string)
@@ -260,7 +265,7 @@ func ConnectOpenIDPost(ctx *context.Context) {
 	ctx.Data["Title"] = "OpenID connect"
 	ctx.Data["PageIsSignIn"] = true
 	ctx.Data["PageIsOpenIDConnect"] = true
-	ctx.Data["EnableOpenIDSignUp"] = setting.Service.EnableOpenIDSignUp
+	ctx.Data["EnableOpenIDSignUp"] = setting.OpenID.EnableSignUp
 	ctx.Data["OpenID"] = oid
 
 	u, _, err := auth.UserSignIn(ctx, form.UserName, form.Password)
@@ -297,7 +302,7 @@ func RegisterOpenID(ctx *context.Context) {
 	ctx.Data["Title"] = "OpenID signup"
 	ctx.Data["PageIsSignIn"] = true
 	ctx.Data["PageIsOpenIDRegister"] = true
-	ctx.Data["EnableOpenIDSignUp"] = setting.Service.EnableOpenIDSignUp
+	ctx.Data["EnableOpenIDSignUp"] = setting.OpenID.EnableSignUp
 	ctx.Data["AllowOnlyInternalRegistration"] = setting.Service.AllowOnlyInternalRegistration
 	ctx.Data["EnableCaptcha"] = setting.Service.EnableCaptcha
 	ctx.Data["Captcha"] = context.GetImageCaptcha()
@@ -332,7 +337,7 @@ func RegisterOpenIDPost(ctx *context.Context) {
 	ctx.Data["Title"] = "OpenID signup"
 	ctx.Data["PageIsSignIn"] = true
 	ctx.Data["PageIsOpenIDRegister"] = true
-	ctx.Data["EnableOpenIDSignUp"] = setting.Service.EnableOpenIDSignUp
+	ctx.Data["EnableOpenIDSignUp"] = setting.OpenID.EnableSignUp
 	context.SetCaptchaData(ctx)
 	ctx.Data["OpenID"] = oid
 
diff --git a/routers/web/auth/openid_test.go b/routers/web/auth/openid_test.go
new file mode 100644
index 0000000000000..8704dc7f0567a
--- /dev/null
+++ b/routers/web/auth/openid_test.go
@@ -0,0 +1,44 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package auth
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/modules/hostmatcher"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/test"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAllowedOpenIDURI(t *testing.T) {
+	defer test.MockVariableValue(&setting.Service)()
+
+	t.Run("Whitelist", func(t *testing.T) {
+		setting.OpenID.Allowlist = hostmatcher.ParseHostMatchList("openid.WHITELISTED_URIS", "trusted.example.com,*.trusted.net")
+		setting.OpenID.Blocklist = hostmatcher.ParseHostMatchList("openid.BLACKLISTED_URIS", "trusted.example.com,bad.example.com")
+
+		assert.NoError(t, allowedOpenIDURI("https://trusted.example.com/openid"))
+		assert.NoError(t, allowedOpenIDURI("https://sub.trusted.net"))
+		assert.Error(t, allowedOpenIDURI("https://trusted.example.com.evil.org"))
+		assert.Error(t, allowedOpenIDURI("https://bad.example.com"))
+	})
+
+	t.Run("Blacklist", func(t *testing.T) {
+		setting.OpenID.Allowlist = nil
+		setting.OpenID.Blocklist = hostmatcher.ParseHostMatchList("openid.BLACKLISTED_URIS", "bad.example.com,10.0.0.0/8")
+
+		assert.Error(t, allowedOpenIDURI("https://bad.example.com"))
+		assert.Error(t, allowedOpenIDURI("https://10.1.1.1"))
+		assert.NoError(t, allowedOpenIDURI("https://good.example.com"))
+	})
+
+	t.Run("InvalidURI", func(t *testing.T) {
+		setting.OpenID.Allowlist = nil
+		setting.OpenID.Blocklist = nil
+
+		assert.Error(t, allowedOpenIDURI("://bad"))
+	})
+}
diff --git a/routers/web/web.go b/routers/web/web.go
index d973064b22913..809801511824b 100644
--- a/routers/web/web.go
+++ b/routers/web/web.go
@@ -299,14 +299,14 @@ func registerWebRoutes(m *web.Router) {
 	validation.AddBindingRules()
 
 	openIDSignInEnabled := func(ctx *context.Context) {
-		if !setting.Service.EnableOpenIDSignIn {
+		if !setting.OpenID.EnableSignIn {
 			ctx.HTTPError(http.StatusForbidden)
 			return
 		}
 	}
 
 	openIDSignUpEnabled := func(ctx *context.Context) {
-		if !setting.Service.EnableOpenIDSignUp {
+		if !setting.OpenID.EnableSignUp {
 			ctx.HTTPError(http.StatusForbidden)
 			return
 		}
diff --git a/services/auth/sspi.go b/services/auth/sspi.go
index 64507539359c6..6b51977430836 100644
--- a/services/auth/sspi.go
+++ b/services/auth/sspi.go
@@ -84,7 +84,7 @@ func (s *SSPI) Verify(req *http.Request, w http.ResponseWriter, store DataStore,
 		store.GetData()["Flash"] = map[string]string{
 			"ErrorMsg": err.Error(),
 		}
-		store.GetData()["EnableOpenIDSignIn"] = setting.Service.EnableOpenIDSignIn
+		store.GetData()["EnableOpenIDSignIn"] = setting.OpenID.EnableSignIn
 		store.GetData()["EnableSSPI"] = true
 		// in this case, the Verify function is called in Gitea's web context
 		// FIXME: it doesn't look good to render the page here, why not redirect?
diff --git a/templates/admin/config.tmpl b/templates/admin/config.tmpl
index 6dc6e0d5ea1eb..4fbff8bf54af2 100644
--- a/templates/admin/config.tmpl
+++ b/templates/admin/config.tmpl
@@ -138,9 +138,9 @@
 				<dt>{{ctx.Locale.Tr "admin.config.show_registration_button"}}</dt>
 				<dd>{{svg (Iif .Service.ShowRegistrationButton "octicon-check" "octicon-x")}}</dd>
 				<dt>{{ctx.Locale.Tr "admin.config.enable_openid_signup"}}</dt>
-				<dd>{{svg (Iif .Service.EnableOpenIDSignUp "octicon-check" "octicon-x")}}</dd>
+				<dd>{{svg (Iif .OpenID.EnableSignUp "octicon-check" "octicon-x")}}</dd>
 				<dt>{{ctx.Locale.Tr "admin.config.enable_openid_signin"}}</dt>
-				<dd>{{svg (Iif .Service.EnableOpenIDSignIn "octicon-check" "octicon-x")}}</dd>
+				<dd>{{svg (Iif .OpenID.EnableSignIn "octicon-check" "octicon-x")}}</dd>
 				<dt>{{ctx.Locale.Tr "admin.config.require_sign_in_view"}}</dt>
 				<dd>{{svg (Iif .Service.RequireSignInViewStrict "octicon-check" "octicon-x")}}</dd>
 				<dt>{{ctx.Locale.Tr "admin.config.mail_notify"}}</dt>