diff --git a/cmds/stagefright/muxer.cpp b/cmds/stagefright/muxer.cpp
index bc7e41e..185491f 100644
--- a/cmds/stagefright/muxer.cpp
+++ b/cmds/stagefright/muxer.cpp
@@ -78,10 +78,14 @@
     int fd = open(outputFileName, O_CREAT | O_LARGEFILE | O_TRUNC | O_RDWR, S_IRUSR | S_IWUSR);
 
     if (fd < 0) {
-        ALOGE("couldn't open file");
-        return fd;
+        ALOGE("couldn't open output file %s", outputFileName);
+        return 1;
     }
-    sp<MediaMuxer> muxer = new MediaMuxer(fd, container);
+    sp<MediaMuxer> muxer = MediaMuxer::create(fd, container);
+    if (muxer == nullptr) {
+        fprintf(stderr, "unable to instantiate muxer for format %d\n", container);
+        return 1;
+    }
     close(fd);
 
     size_t trackCount = extractor->countTracks();
diff --git a/media/libstagefright/MediaAppender.cpp b/media/libstagefright/MediaAppender.cpp
index 21dcfa1..2d9c651 100644
--- a/media/libstagefright/MediaAppender.cpp
+++ b/media/libstagefright/MediaAppender.cpp
@@ -308,7 +308,11 @@
         ALOGE("MediaAppender::start() is called in invalid state %d", mState);
         return INVALID_OPERATION;
     }
-    mMuxer = new (std::nothrow) MediaMuxer(mFd, mFormat);
+    mMuxer = MediaMuxer::create(mFd, mFormat);
+    if (mMuxer == nullptr) {
+        ALOGE("MediaMuxer::create failed");
+        return INVALID_OPERATION;
+    }
     for (const auto& n : mFmtIndexMap) {
         ssize_t muxIndex = mMuxer->addTrack(n.second);
         if (muxIndex < 0) {
diff --git a/media/libstagefright/MediaMuxer.cpp b/media/libstagefright/MediaMuxer.cpp
index 80f705b..9768f97 100644
--- a/media/libstagefright/MediaMuxer.cpp
+++ b/media/libstagefright/MediaMuxer.cpp
@@ -46,6 +46,30 @@
            format == MediaMuxer::OUTPUT_FORMAT_HEIF;
 }
 
+MediaMuxer* MediaMuxer::create(int fd, OutputFormat format) {
+    bool isInputValid = true;
+    if (isMp4Format(format)) {
+        isInputValid = MPEG4Writer::isFdOpenModeValid(fd);
+    } else if (format == OUTPUT_FORMAT_WEBM) {
+        isInputValid = WebmWriter::isFdOpenModeValid(fd);
+    } else if (format == OUTPUT_FORMAT_OGG) {
+        isInputValid = OggWriter::isFdOpenModeValid(fd);
+    } else {
+        ALOGE("MediaMuxer does not support output format %d", format);
+        return nullptr;
+    }
+    if (!isInputValid) {
+        ALOGE("File descriptor is not suitable for format %d", format);
+        return nullptr;
+    }
+
+    MediaMuxer *muxer = new (std::nothrow) MediaMuxer(fd, (MediaMuxer::OutputFormat)format);
+    if (muxer == nullptr) {
+        ALOGE("Failed to create writer object");
+    }
+    return muxer;
+}
+
 MediaMuxer::MediaMuxer(int fd, OutputFormat format)
     : mFormat(format),
       mState(UNINITIALIZED) {
diff --git a/media/libstagefright/include/media/stagefright/MediaMuxer.h b/media/libstagefright/include/media/stagefright/MediaMuxer.h
index e97a65e..6dc70bf 100644
--- a/media/libstagefright/include/media/stagefright/MediaMuxer.h
+++ b/media/libstagefright/include/media/stagefright/MediaMuxer.h
@@ -48,6 +48,14 @@
 // deleting the output file after stop.
 struct MediaMuxer : public MediaMuxerBase {
 public:
+    /**
+     * Creates the muxer for a given output format.
+     * @param fd : file descriptor of the output file.
+     * @param format : output format of the muxer. e.g.: webm/mp4/ogg
+     * @return writer's object or nullptr if error.
+     */
+    static MediaMuxer* create(int fd, OutputFormat format);
+
     // Construct the muxer with the file descriptor. Note that the MediaMuxer
     // will close this file at stop().
     MediaMuxer(int fd, OutputFormat format);
diff --git a/media/libstagefright/include/media/stagefright/MediaWriter.h b/media/libstagefright/include/media/stagefright/MediaWriter.h
index 9f20185..2b14811 100644
--- a/media/libstagefright/include/media/stagefright/MediaWriter.h
+++ b/media/libstagefright/include/media/stagefright/MediaWriter.h
@@ -31,6 +31,29 @@
           mMaxFileDurationLimitUs(0) {
     }
 
+    // Returns true if the file descriptor is opened using a mode
+    // which meets minimum writer/muxer requirements.
+    static bool isFdOpenModeValid(int fd) {
+        // check for invalid file descriptor.
+        int flags = fcntl(fd, F_GETFL);
+        if (flags == -1) {
+            ALOGE("Invalid File Status Flags and/or mode : %d", flags);
+            return false;
+        }
+        // fd must be in read-write mode or write-only mode.
+        if ((flags & (O_RDWR | O_WRONLY)) == 0) {
+            ALOGE("File must be writable");
+            return false;
+        }
+        // Verify fd is seekable
+        off64_t off = lseek64(fd, 0, SEEK_SET);
+        if (off < 0) {
+            ALOGE("File descriptor is not seekable");
+            return false;
+        }
+        return true;
+    }
+
     virtual status_t addSource(const sp<MediaSource> &source) = 0;
     virtual bool reachedEOS() = 0;
     virtual status_t start(MetaData *params = NULL) = 0;
diff --git a/media/libstagefright/tests/fuzzers/MediaMuxerFuzzer.cpp b/media/libstagefright/tests/fuzzers/MediaMuxerFuzzer.cpp
index 5df3267..70d73c8 100644
--- a/media/libstagefright/tests/fuzzers/MediaMuxerFuzzer.cpp
+++ b/media/libstagefright/tests/fuzzers/MediaMuxerFuzzer.cpp
@@ -52,7 +52,10 @@
 
   MediaMuxer::OutputFormat format =
       (MediaMuxer::OutputFormat)fdp.ConsumeIntegralInRange<int32_t>(0, 4);
-  sp<MediaMuxer> mMuxer(new MediaMuxer(fd, format));
+  sp<MediaMuxer> mMuxer = MediaMuxer::create(fd, format);
+  if (mMuxer == nullptr) {
+    return 0;
+  }
 
   while (fdp.remaining_bytes() > 1) {
     switch (fdp.ConsumeIntegralInRange<uint8_t>(0, 4)) {
diff --git a/media/libstagefright/webm/WebmWriter.cpp b/media/libstagefright/webm/WebmWriter.cpp
index 5eaadbd..3823c36 100644
--- a/media/libstagefright/webm/WebmWriter.cpp
+++ b/media/libstagefright/webm/WebmWriter.cpp
@@ -54,6 +54,19 @@
 
 static const int64_t kMinStreamableFileSizeInBytes = 5 * 1024 * 1024;
 
+bool WebmWriter::isFdOpenModeValid(int fd) {
+    // check for invalid file descriptor.
+    if (!MediaWriter::isFdOpenModeValid(fd)) {
+        return false;
+    }
+    int flags = fcntl(fd, F_GETFL);
+    if ((flags & O_RDWR) == 0) {
+        ALOGE("File must be in read-write mode for webm writer");
+        return false;
+    }
+    return true;
+}
+
 WebmWriter::WebmWriter(int fd)
     : mFd(dup(fd)),
       mInitCheck(mFd < 0 ? NO_INIT : OK),
diff --git a/media/libstagefright/webm/include/webm/WebmWriter.h b/media/libstagefright/webm/include/webm/WebmWriter.h
index ed5bc4c..e339add 100644
--- a/media/libstagefright/webm/include/webm/WebmWriter.h
+++ b/media/libstagefright/webm/include/webm/WebmWriter.h
@@ -36,6 +36,10 @@
 
 class WebmWriter : public MediaWriter {
 public:
+    // Returns true if the file descriptor is opened using a mode
+    // which is compatible with WebmWriter.
+    // Note that this overloads that method in the base class.
+    static bool isFdOpenModeValid(int fd);
     explicit WebmWriter(int fd);
     ~WebmWriter() { reset(); }
 
diff --git a/media/ndk/NdkMediaMuxer.cpp b/media/ndk/NdkMediaMuxer.cpp
index 1965e62..9d62884 100644
--- a/media/ndk/NdkMediaMuxer.cpp
+++ b/media/ndk/NdkMediaMuxer.cpp
@@ -46,7 +46,7 @@
     if (mData == nullptr) {
         return nullptr;
     }
-    mData->mImpl = new (std::nothrow) MediaMuxer(fd, (android::MediaMuxer::OutputFormat)format);
+    mData->mImpl = MediaMuxer::create(fd, (MediaMuxer::OutputFormat)format);
     if (mData->mImpl == nullptr) {
         delete mData;
         return nullptr;
diff --git a/services/camera/libcameraservice/api2/HeicCompositeStream.cpp b/services/camera/libcameraservice/api2/HeicCompositeStream.cpp
index 54cc27a..71965f2 100644
--- a/services/camera/libcameraservice/api2/HeicCompositeStream.cpp
+++ b/services/camera/libcameraservice/api2/HeicCompositeStream.cpp
@@ -931,7 +931,7 @@
                 tempOutputFile.str().c_str(), errno);
         return NO_INIT;
     }
-    inputFrame.muxer = new MediaMuxer(inputFrame.fileFd, MediaMuxer::OUTPUT_FORMAT_HEIF);
+    inputFrame.muxer = MediaMuxer::create(inputFrame.fileFd, MediaMuxer::OUTPUT_FORMAT_HEIF);
     if (inputFrame.muxer == nullptr) {
         ALOGE("%s: Failed to create MediaMuxer for file fd %d",
                 __FUNCTION__, inputFrame.fileFd);