diff --git a/extensions/browser/src/browser/paths.test.ts b/extensions/browser/src/browser/paths.test.ts
index bbf651e657f..9489d681c85 100644
--- a/extensions/browser/src/browser/paths.test.ts
+++ b/extensions/browser/src/browser/paths.test.ts
@@ -345,6 +345,24 @@ describe("resolveExistingUploadPaths", () => {
     });
   });
 
+  it("rejects traversal-shaped inbound media URI references before URL normalization", async () => {
+    await withFixtureRoot(async ({ inboundMediaDir, uploadsDir }) => {
+      const inboundFile = path.join(inboundMediaDir, "report.pdf");
+      await fs.writeFile(inboundFile, "pdf", "utf8");
+
+      const result = await resolveExistingUploadPaths({
+        uploadDir: uploadsDir,
+        inboundMediaDir,
+        requestedPaths: ["media://inbound/nested/../report.pdf"],
+      });
+
+      expect(result.ok).toBe(false);
+      if (!result.ok) {
+        expect(result.error).toContain("Invalid media reference");
+      }
+    });
+  });
+
   it("rejects nested absolute inbound media paths", async () => {
     await withFixtureRoot(async ({ inboundMediaDir, uploadsDir }) => {
       const nestedDir = path.join(inboundMediaDir, "nested");
diff --git a/extensions/browser/src/browser/paths.ts b/extensions/browser/src/browser/paths.ts
index 3d301fc4ded..994e99cc84a 100644
--- a/extensions/browser/src/browser/paths.ts
+++ b/extensions/browser/src/browser/paths.ts
@@ -94,6 +94,8 @@ function resolveManagedInboundMediaRef(
   }
 
   if (/^media:\/\//i.test(normalizedSource)) {
+    const rawUriMatch = /^media:\/\/[^/?#]*([^?#]*)/iu.exec(normalizedSource);
+    const rawPath = rawUriMatch?.[1] ?? "";
     let parsed: URL;
     try {
       parsed = new URL(normalizedSource);
@@ -106,7 +108,10 @@ function resolveManagedInboundMediaRef(
         error: `Unsupported media reference location: ${parsed.hostname || "(missing)"}`,
       };
     }
-    const decoded = decodeInboundMediaId(parsed.pathname.replace(/^\/+/, ""), normalizedSource);
+    if (!rawPath.startsWith("/") || rawPath.slice(1).includes("/") || rawPath.includes("\\")) {
+      return { ok: false, error: `Invalid media reference: ${normalizedSource}` };
+    }
+    const decoded = decodeInboundMediaId(rawPath.slice(1), normalizedSource);
     return decoded?.ok
       ? {
           ok: true,