diff --git a/weed/command/s3.go b/weed/command/s3.go
index faedfe520..1cb0b8780 100644
--- a/weed/command/s3.go
+++ b/weed/command/s3.go
@@ -29,6 +29,7 @@ import (
 	stats_collect "github.com/seaweedfs/seaweedfs/weed/stats"
 	"github.com/seaweedfs/seaweedfs/weed/util"
 	"github.com/seaweedfs/seaweedfs/weed/util/grace"
+	util_http "github.com/seaweedfs/seaweedfs/weed/util/http"
 	"github.com/seaweedfs/seaweedfs/weed/util/version"
 )
 
@@ -524,6 +525,9 @@ func (s3opt *S3Options) startS3Server() bool {
 // startIcebergServer starts the Iceberg REST Catalog server on a separate port.
 func (s3opt *S3Options) startIcebergServer(s3ApiServer *s3api.S3ApiServer) {
 	icebergRouter := mux.NewRouter().SkipClean(true)
+	// warehouse/parent query values may legally contain ';', which Go's
+	// url.ParseQuery would otherwise drop
+	icebergRouter.Use(util_http.EscapeSemicolonsInQuery)
 
 	// Create Iceberg server using the S3ApiServer as filer client
 	icebergServer := iceberg.NewServer(s3ApiServer, s3ApiServer)
diff --git a/weed/iamapi/iamapi_server.go b/weed/iamapi/iamapi_server.go
index 49138956a..26218587f 100644
--- a/weed/iamapi/iamapi_server.go
+++ b/weed/iamapi/iamapi_server.go
@@ -22,6 +22,7 @@ import (
 	. "github.com/seaweedfs/seaweedfs/weed/s3api/s3_constants"
 	"github.com/seaweedfs/seaweedfs/weed/s3api/s3err"
 	"github.com/seaweedfs/seaweedfs/weed/util"
+	util_http "github.com/seaweedfs/seaweedfs/weed/util/http"
 	"github.com/seaweedfs/seaweedfs/weed/util/request_id"
 	"github.com/seaweedfs/seaweedfs/weed/wdclient"
 	"google.golang.org/grpc"
@@ -117,6 +118,9 @@ func NewIamApiServerWithStore(router *mux.Router, option *IamServerOption, expli
 }
 
 func (iama *IamApiServer) registerRouter(router *mux.Router) {
+	// SigV4 recomputes the canonical query from the parsed query, so raw ';'
+	// pairs that Go would drop must be recovered before verification.
+	router.Use(util_http.EscapeSemicolonsInQuery)
 	// API Router
 	apiRouter := router.PathPrefix("/").Subrouter()
 	apiRouter.Use(request_id.Middleware)
diff --git a/weed/s3api/auth_presigned_semicolon_test.go b/weed/s3api/auth_presigned_semicolon_test.go
new file mode 100644
index 000000000..9dfc1a703
--- /dev/null
+++ b/weed/s3api/auth_presigned_semicolon_test.go
@@ -0,0 +1,45 @@
+package s3api
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/seaweedfs/seaweedfs/weed/s3api/s3err"
+	util_http "github.com/seaweedfs/seaweedfs/weed/util/http"
+)
+
+// A presigned URL that signs content-type carries
+// X-Amz-SignedHeaders=content-type%3Bhost. Some clients and proxies decode
+// the %3B into a raw ';', which RFC 3986 permits in a query string and AWS
+// accepts, but Go's url.ParseQuery drops the whole pair — verification then
+// fails with MissingFields. The router middleware re-encodes the ';' so the
+// parameter survives.
+func TestPresignedPutSignedContentTypeWithRawSemicolon(t *testing.T) {
+	iam := newTestIAM()
+
+	req, err := newTestRequest(http.MethodPut, "http://127.0.0.1:9000/bucket/key.png", 0, nil)
+	if err != nil {
+		t.Fatalf("newTestRequest: %v", err)
+	}
+	req.Header.Set("Content-Type", "image/png")
+	if err := preSignV4WithHeaders(iam, req, "AKIAIOSFODNN7EXAMPLE", "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY", 600, []string{"host", "content-type"}); err != nil {
+		t.Fatalf("preSignV4WithHeaders: %v", err)
+	}
+	req.URL.RawQuery = strings.ReplaceAll(req.URL.RawQuery, "%3B", ";")
+
+	if _, errCode := iam.reqSignatureV4Verify(req); errCode == s3err.ErrNone {
+		t.Fatal("raw-semicolon query unexpectedly verified without normalization")
+	}
+
+	errCode := s3err.ErrInternalError
+	handler := util_http.EscapeSemicolonsInQuery(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, errCode = iam.reqSignatureV4Verify(r)
+	}))
+	handler.ServeHTTP(httptest.NewRecorder(), req)
+
+	if errCode != s3err.ErrNone {
+		t.Fatalf("expected ErrNone through semicolon-normalizing middleware, got %v", errCode)
+	}
+}
diff --git a/weed/s3api/s3api_server.go b/weed/s3api/s3api_server.go
index 96028a3e4..5943bfeca 100644
--- a/weed/s3api/s3api_server.go
+++ b/weed/s3api/s3api_server.go
@@ -724,6 +724,8 @@ func (s3a *S3ApiServer) UnifiedPostHandler(w http.ResponseWriter, r *http.Reques
 }
 
 func (s3a *S3ApiServer) registerRouter(router *mux.Router) {
+	// runs before subrouter matching so Queries() matchers see the fixed query
+	router.Use(util_http.EscapeSemicolonsInQuery)
 	// API Router
 	apiRouter := router.PathPrefix("/").Subrouter()
 	apiRouter.Use(request_id.Middleware)
diff --git a/weed/util/http/query_middleware.go b/weed/util/http/query_middleware.go
new file mode 100644
index 000000000..3870e0c8a
--- /dev/null
+++ b/weed/util/http/query_middleware.go
@@ -0,0 +1,25 @@
+package http
+
+import (
+	"net/http"
+	"strings"
+)
+
+// EscapeSemicolonsInQuery re-encodes raw ';' in the query string. RFC 3986
+// allows ';' in a query and AWS treats it as data, but Go's url.ParseQuery
+// drops every key=value pair containing one. Presigned URLs carry
+// X-Amz-SignedHeaders=content-type%3Bhost; clients that decode the %3B would
+// otherwise lose the parameter entirely and fail signature verification.
+func EscapeSemicolonsInQuery(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if strings.Contains(r.URL.RawQuery, ";") {
+			u := *r.URL
+			u.RawQuery = strings.ReplaceAll(u.RawQuery, ";", "%3B")
+			r2 := new(http.Request)
+			*r2 = *r
+			r2.URL = &u
+			r = r2
+		}
+		next.ServeHTTP(w, r)
+	})
+}