--- a/netwerk/streamconv/converters/nsHTTPCompressConv.cpp	
+++ a/netwerk/streamconv/converters/nsHTTPCompressConv.cpp	
@@ -160,31 +160,36 @@ nsHTTPCompressConv::OnStopRequest(nsIReq
 NS_METHOD
 nsHTTPCompressConv::BrotliHandler(nsIInputStream *stream, void *closure, const char *dataIn,
                                   uint32_t, uint32_t aAvail, uint32_t *countRead)
 {
   MOZ_ASSERT(stream);
   nsHTTPCompressConv *self = static_cast<nsHTTPCompressConv *>(closure);
   *countRead = 0;
 
-  const uint32_t kOutSize = 128 * 1024; // just a chunk size, we call in a loop
-  unsigned char outBuffer[kOutSize];
-  unsigned char *outPtr;
+  const size_t kOutSize = 128 * 1024; // just a chunk size, we call in a loop
+  uint8_t *outPtr;
   size_t outSize;
   size_t avail = aAvail;
   BrotliResult res;
 
   if (!self->mBrotli) {
     *countRead = aAvail;
     return NS_OK;
   }
 
+  auto outBuffer = MakeUniqueFallible<uint8_t[]>(kOutSize);
+  if (outBuffer == nullptr) {
+    self->mBrotli->mStatus = NS_ERROR_OUT_OF_MEMORY;
+    return self->mBrotli->mStatus;
+  }
+
   do {
     outSize = kOutSize;
-    outPtr = outBuffer;
+    outPtr = outBuffer.get();
 
     // brotli api is documented in brotli/dec/decode.h and brotli/dec/decode.c
     LOG(("nsHttpCompresssConv %p brotlihandler decompress %d\n", self, avail));
     res = ::BrotliDecompressStream(
       &avail, reinterpret_cast<const unsigned char **>(&dataIn),
       &outSize, &outPtr, &self->mBrotli->mTotalOut, &self->mBrotli->mState);
     outSize = kOutSize - outSize;
     LOG(("nsHttpCompresssConv %p brotlihandler decompress rv=%x out=%d\n",
@@ -205,17 +210,17 @@ nsHTTPCompressConv::BrotliHandler(nsIInp
         self->mBrotli->mStatus = NS_ERROR_UNEXPECTED;
         return self->mBrotli->mStatus;
       }
     }
     if (outSize > 0) {
       nsresult rv = self->do_OnDataAvailable(self->mBrotli->mRequest,
                                              self->mBrotli->mContext,
                                              self->mBrotli->mSourceOffset,
-                                             reinterpret_cast<const char *>(outBuffer),
+                                             reinterpret_cast<const char *>(outBuffer.get()),
                                              outSize);
       LOG(("nsHttpCompressConv %p BrotliHandler ODA rv=%x", self, rv));
       if (NS_FAILED(rv)) {
         self->mBrotli->mStatus = rv;
         return self->mBrotli->mStatus;
       }
     }