diff --git a/src/media/video-dimensions.test.ts b/src/media/video-dimensions.test.ts
index b82f5bed2ba8..c8480c181745 100644
--- a/src/media/video-dimensions.test.ts
+++ b/src/media/video-dimensions.test.ts
@@ -26,6 +26,12 @@ describe("parseFfprobeVideoDimensions", () => {
       parseFfprobeVideoDimensions(JSON.stringify({ streams: [{ width: 720.5, height: 1280 }] })),
     ).toBeUndefined();
   });
+
+  it("returns undefined for malformed JSON instead of throwing", () => {
+    for (const stdout of ["{", "", "not json", "null", "42", '"text"', '{"streams":{}}']) {
+      expect(parseFfprobeVideoDimensions(stdout)).toBeUndefined();
+    }
+  });
 });
 
 describe("probeVideoDimensions", () => {
diff --git a/src/media/video-dimensions.ts b/src/media/video-dimensions.ts
index 1e0830dd0052..8c65370117be 100644
--- a/src/media/video-dimensions.ts
+++ b/src/media/video-dimensions.ts
@@ -16,10 +16,23 @@ function parsePositiveDimension(value: unknown): number | undefined {
 
 /** Parses ffprobe JSON output, accepting only positive integer first-stream dimensions. */
 export function parseFfprobeVideoDimensions(stdout: string): VideoDimensions | undefined {
-  const parsed = JSON.parse(stdout) as { streams?: Array<{ width?: unknown; height?: unknown }> };
-  const stream = parsed.streams?.[0];
-  const width = parsePositiveDimension(stream?.width);
-  const height = parsePositiveDimension(stream?.height);
+  let parsed: unknown;
+  try {
+    parsed = JSON.parse(stdout);
+  } catch {
+    return undefined;
+  }
+  if (!parsed || typeof parsed !== "object") {
+    return undefined;
+  }
+  const streams = (parsed as { streams?: unknown }).streams;
+  const stream = Array.isArray(streams) ? streams[0] : undefined;
+  if (!stream || typeof stream !== "object") {
+    return undefined;
+  }
+  const record = stream as Record<string, unknown>;
+  const width = parsePositiveDimension(record.width);
+  const height = parsePositiveDimension(record.height);
   return width && height ? { width, height } : undefined;
 }