diff --git a/middleware/cache/cache.go b/middleware/cache/cache.go
index 70d08dcae6a..f44be493e8a 100644
--- a/middleware/cache/cache.go
+++ b/middleware/cache/cache.go
@@ -905,7 +905,9 @@ func New(config ...Config) fiber.Handler {
 	}
 }
 
-// hasDirective checks if a cache-control header contains a directive (case-insensitive)
+// hasDirective checks if a cache directive header value contains a directive (case-insensitive).
+// A directive is considered matched when followed by end-of-string, ',', ' ', '\t', or '='
+// per RFC 9111 §5.2.
 func hasDirective(cc, directive string) bool {
 	ccLen := len(cc)
 	dirLen := len(directive)
@@ -915,11 +917,15 @@ func hasDirective(cc, directive string) bool {
 		}
 		if i > 0 {
 			prev := cc[i-1]
-			if prev != ' ' && prev != ',' {
+			if prev != ' ' && prev != ',' && prev != '\t' {
 				continue
 			}
 		}
-		if i+dirLen == ccLen || cc[i+dirLen] == ',' {
+		if i+dirLen == ccLen {
+			return true
+		}
+		next := cc[i+dirLen]
+		if next == ',' || next == ' ' || next == '\t' || next == '=' {
 			return true
 		}
 	}
diff --git a/middleware/cache/cache_test.go b/middleware/cache/cache_test.go
index 24d50617c9a..439af2b74b9 100644
--- a/middleware/cache/cache_test.go
+++ b/middleware/cache/cache_test.go
@@ -5091,3 +5091,47 @@ func Test_Cache_ConfigurationAndResponseHandling(t *testing.T) {
 		require.Equal(t, cacheMiss, rsp2.Header.Get("X-Cache"))
 	})
 }
+
+func Test_hasDirective(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name      string
+		cc        string
+		directive string
+		want      bool
+	}{
+		// Basic matches
+		{"exact match", "no-cache", "no-cache", true},
+		{"comma separated", "public, no-cache, max-age=0", "no-cache", true},
+		{"at start", "no-cache, max-age=0", "no-cache", true},
+		{"at end", "public, no-cache", "no-cache", true},
+		{"not present", "public, max-age=0", "no-cache", false},
+		{"partial match", "no-cach", "no-cache", false},
+		{"substring of longer token", "no-cache-extended", "no-cache", false},
+
+		// Trailing whitespace (#4143)
+		{"trailing space", "no-cache ", "no-cache", true},
+		{"trailing tab", "no-cache\t", "no-cache", true},
+		{"private trailing space", "private ", "private", true},
+
+		// Directive with value (#4143)
+		{"directive with equals", `no-cache="Set-Cookie"`, "no-cache", true},
+		{"max-age with value", "max-age=3600", "max-age", true},
+		{"s-maxage with value in list", "public, s-maxage=600, max-age=3600", "s-maxage", true},
+
+		// Tab as separator before directive
+		{"tab before directive", "public,\tno-cache", "no-cache", true},
+
+		// Case insensitive
+		{"case insensitive", "No-Cache", "no-cache", true},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+			got := hasDirective(tc.cc, tc.directive)
+			require.Equal(t, tc.want, got)
+		})
+	}
+}