diff --git a/go.mod b/go.mod
index a5f42c6cafc..9d23a994104 100644
--- a/go.mod
+++ b/go.mod
@@ -105,6 +105,7 @@ require (
 	go.yaml.in/yaml/v4 v4.0.0-rc.5
 	golang.org/x/crypto v0.53.0
 	golang.org/x/image v0.42.0
+	golang.org/x/mod v0.37.0
 	golang.org/x/net v0.56.0
 	golang.org/x/oauth2 v0.36.0
 	golang.org/x/sync v0.21.0
@@ -267,7 +268,6 @@ require (
 	go.uber.org/zap/exp v0.3.0 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	go4.org v0.0.0-20260112195520-a5071408f32f // indirect
-	golang.org/x/mod v0.37.0 // indirect
 	golang.org/x/time v0.15.0 // indirect
 	golang.org/x/tools v0.45.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20260610212136-7ab31c22f7ad // indirect
diff --git a/modules/packages/goproxy/metadata.go b/modules/packages/goproxy/metadata.go
index b19738db56d..db50ac7faa3 100644
--- a/modules/packages/goproxy/metadata.go
+++ b/modules/packages/goproxy/metadata.go
@@ -10,6 +10,8 @@ import (
 	"strings"
 
 	"gitea.dev/modules/util"
+
+	"golang.org/x/mod/semver"
 )
 
 const (
@@ -20,6 +22,7 @@ const (
 
 var (
 	ErrInvalidStructure  = util.NewInvalidArgumentErrorf("package has invalid structure")
+	ErrInvalidVersion    = util.NewInvalidArgumentErrorf("package version is invalid")
 	ErrGoModFileTooLarge = util.NewInvalidArgumentErrorf("go.mod file is too large")
 )
 
@@ -54,6 +57,13 @@ func ParsePackage(r io.ReaderAt, size int64) (*Package, error) {
 				Name:    strings.TrimSuffix(nameAndVersion, "@"+parts[1]),
 				Version: versionParts[0],
 			}
+
+			// the version is taken verbatim from the zip path and later written
+			// one per line into the @v/list proxy response, so it has to be a
+			// valid module version (no newlines or other stray characters)
+			if !semver.IsValid(p.Version) {
+				return nil, ErrInvalidVersion
+			}
 		}
 
 		if len(versionParts) > 1 {
diff --git a/modules/packages/goproxy/metadata_test.go b/modules/packages/goproxy/metadata_test.go
index 4e7f394f8bc..24db3596510 100644
--- a/modules/packages/goproxy/metadata_test.go
+++ b/modules/packages/goproxy/metadata_test.go
@@ -59,6 +59,16 @@ func TestParsePackage(t *testing.T) {
 		assert.Equal(t, "module gitea.com/go-gitea/gitea", p.GoMod)
 	})
 
+	t.Run("InvalidVersion", func(t *testing.T) {
+		data := createArchive(map[string][]byte{
+			packageName + "@v1.0.0\nv99.0.0/go.mod": []byte("module " + packageName),
+		})
+
+		p, err := ParsePackage(data, int64(data.Len()))
+		assert.Nil(t, p)
+		assert.ErrorIs(t, err, ErrInvalidVersion)
+	})
+
 	t.Run("Valid", func(t *testing.T) {
 		data := createArchive(map[string][]byte{
 			packageName + "@" + packageVersion + "/subdir/go.mod": []byte("invalid"),