diff --git a/changelog.d/chunked_gelf_limit_handling.fix.md b/changelog.d/chunked_gelf_limit_handling.fix.md
new file mode 100644
index 0000000000000..ec92278e162f3
--- /dev/null
+++ b/changelog.d/chunked_gelf_limit_handling.fix.md
@@ -0,0 +1,3 @@
+Fixed two problems with the `chunked_gelf` framing decoder's limits. `pending_messages_limit` was applied to every chunk rather than only to new messages, so once the limit was reached even chunks of messages already pending were rejected and those messages could never complete. Separately, dropping a message for exceeding `max_length` left its timeout task running, so the number of live tasks was not bounded by `pending_messages_limit` the way the pending message count was.
+
+authors: pront
diff --git a/changelog.d/chunked_gelf_one_byte_panic.fix.md b/changelog.d/chunked_gelf_one_byte_panic.fix.md
new file mode 100644
index 0000000000000..0d936fcbe30b9
--- /dev/null
+++ b/changelog.d/chunked_gelf_one_byte_panic.fix.md
@@ -0,0 +1,3 @@
+Fixed a panic in the `chunked_gelf` framing decoder when a one-byte message arrived and trace-level logging was enabled for it, which took down the source. Such a message is now passed on for the decoder to reject, as any other malformed payload would be.
+
+authors: pront
diff --git a/lib/codecs/src/decoding/framing/chunked_gelf.rs b/lib/codecs/src/decoding/framing/chunked_gelf.rs
index f469e3f5cdb52..1f3046df064d7 100644
--- a/lib/codecs/src/decoding/framing/chunked_gelf.rs
+++ b/lib/codecs/src/decoding/framing/chunked_gelf.rs
@@ -137,7 +137,7 @@ impl MessageState {
         let chunk_bitmap_id = 1 << sequence_number;
         self.chunks_bitmap |= chunk_bitmap_id;
         self.current_length += chunk.remaining();
-        self.chunks[sequence_number as usize] = chunk;
+        self.chunks[sequence_number as usize] = Bytes::copy_from_slice(&chunk);
     }
 
     fn is_complete(&self) -> bool {
@@ -148,18 +148,20 @@ impl MessageState {
         self.current_length
     }
 
-    fn retrieve_message(&self) -> Option<Bytes> {
-        if self.is_complete() {
-            self.timeout_task.abort();
-            let chunks = &self.chunks[0..self.total_chunks as usize];
-            let mut message = BytesMut::new();
-            for chunk in chunks {
-                message.extend_from_slice(chunk);
-            }
-            Some(message.freeze())
-        } else {
-            None
+    /// Peak is ~2x the message: a contiguous destination coexists with the chunks it copies
+    /// from. Reserving exactly keeps a growing buffer from adding slack on top of that.
+    fn retrieve_message(&mut self) -> Option<Bytes> {
+        if !self.is_complete() {
+            return None;
+        }
+
+        self.timeout_task.abort();
+        let mut message = BytesMut::with_capacity(self.current_length);
+        for chunk in &mut self.chunks[0..self.total_chunks as usize] {
+            message.extend_from_slice(chunk);
+            *chunk = Bytes::new();
         }
+        Some(message.freeze())
     }
 }
 
@@ -295,7 +297,7 @@ pub struct ChunkedGelfDecoder {
     // message, so we have to read all the bytes from the message (datagram)
     bytes_decoder: BytesDecoder,
     decompression_config: ChunkedGelfDecompressionConfig,
-    state: Arc<Mutex<HashMap<u64, MessageState>>>,
+    state: Arc<Mutex<HashMap<u64, Box<MessageState>>>>,
     timeout: Duration,
     pending_messages_limit: Option<usize>,
     max_length: Option<usize>,
@@ -367,7 +369,12 @@ impl ChunkedGelfDecoder {
 
         let mut state_lock = self.state.lock().expect("poisoned lock");
 
-        if let Some(pending_messages_limit) = self.pending_messages_limit {
+        // Only a new message grows the table, so the limit applies on insert. Checking it
+        // before the lookup rejected chunks of messages already pending, which could then
+        // never complete and expired instead.
+        if !state_lock.contains_key(&message_id)
+            && let Some(pending_messages_limit) = self.pending_messages_limit
+        {
             ensure!(
                 state_lock.len() < pending_messages_limit,
                 PendingMessagesLimitReachedSnafu {
@@ -394,7 +401,7 @@ impl ChunkedGelfDecoder {
                     );
                 }
             });
-            MessageState::new(total_chunks, timeout_handle)
+            Box::new(MessageState::new(total_chunks, timeout_handle))
         });
 
         ensure!(
@@ -421,7 +428,11 @@ impl ChunkedGelfDecoder {
         if let Some(max_length) = self.max_length {
             let length = message_state.current_length();
             if length > max_length {
-                state_lock.remove(&message_id);
+                // Abort on removal, or the task outlives its entry and the live-task count is
+                // no longer bounded by `pending_messages_limit`.
+                if let Some(dropped) = state_lock.remove(&message_id) {
+                    dropped.timeout_task.abort();
+                }
                 return Err(ChunkedGelfDecoderError::MaxLengthExceed {
                     message_id,
                     sequence_number,
@@ -451,9 +462,11 @@ impl ChunkedGelfDecoder {
             src.advance(2);
             self.decode_chunk(src)?
         } else {
+            // Slice defensively: a frame here is only known to be non-empty, and one shorter
+            // than the magic is reachable from an unauthenticated sender.
             trace!(
-                "Received an unchunked GELF message. First two bytes of message: {:?}",
-                &src[0..2]
+                "Received an unchunked GELF message. First bytes of message: {:?}",
+                &src[..src.len().min(GELF_MAGIC.len())]
             );
             Some(src)
         };
@@ -815,6 +828,21 @@ mod tests {
         ));
     }
 
+    #[rstest]
+    #[case::one_byte(&b"x"[..])]
+    #[case::two_bytes(&b"xy"[..])]
+    #[tokio::test]
+    #[traced_test]
+    async fn decode_short_unchunked_frame_does_not_panic(#[case] payload: &[u8]) {
+        // The trace log on that branch formats two bytes. `traced_test` enables the level.
+        let mut src = BytesMut::from(payload);
+        let mut decoder = ChunkedGelfDecoder::default();
+
+        let frame = decoder.decode_eof(&mut src).expect("must not fail");
+
+        assert_eq!(frame, Some(Bytes::copy_from_slice(payload)));
+    }
+
     #[tokio::test]
     async fn decode_empty_input() {
         let mut src = BytesMut::new();
@@ -917,6 +945,104 @@ mod tests {
         assert!(decoder.state.lock().unwrap().len() == 1);
     }
 
+    #[rstest]
+    #[tokio::test]
+    async fn decode_accepts_chunks_of_pending_messages_at_the_limit(
+        two_chunks_message: ([BytesMut; 2], String),
+        three_chunks_message: ([BytesMut; 3], String),
+    ) {
+        // The limit bounds how many messages may be pending, not which chunks are accepted.
+        let (mut two_chunks, two_chunks_expected) = two_chunks_message;
+        let (mut three_chunks, _) = three_chunks_message;
+        let mut decoder = ChunkedGelfDecoder {
+            pending_messages_limit: Some(1),
+            ..Default::default()
+        };
+
+        let frame = decoder.decode_eof(&mut two_chunks[0]).unwrap();
+        assert!(frame.is_none());
+        assert_eq!(decoder.state.lock().unwrap().len(), 1);
+
+        // The table is full, so a new message id is rejected.
+        assert!(decoder.decode_eof(&mut three_chunks[0]).is_err());
+
+        // ...but the pending message still completes.
+        let frame = decoder.decode_eof(&mut two_chunks[1]).unwrap();
+        assert_eq!(frame, Some(Bytes::from(two_chunks_expected)));
+        assert_eq!(decoder.state.lock().unwrap().len(), 0);
+    }
+
+    #[rstest]
+    #[tokio::test(start_paused = true)]
+    async fn decode_max_length_exceeded_does_not_leak_timeout_task(
+        two_chunks_message: ([BytesMut; 2], String),
+    ) {
+        // An unaborted task outlives its entry, unbounding the live-task count.
+        let (mut chunks, _) = two_chunks_message;
+        let mut decoder = ChunkedGelfDecoder {
+            max_length: Some(5),
+            ..Default::default()
+        };
+
+        assert!(decoder.decode_eof(&mut chunks[0]).unwrap().is_none());
+        let timeout_task = {
+            let state = decoder.state.lock().unwrap();
+            state
+                .values()
+                .next()
+                .map(|message_state| message_state.timeout_task.abort_handle())
+                .expect("a message should be pending")
+        };
+        assert!(!timeout_task.is_finished());
+
+        assert!(decoder.decode_eof(&mut chunks[1]).is_err());
+        assert_eq!(decoder.state.lock().unwrap().len(), 0);
+
+        tokio::task::yield_now().await;
+        assert!(
+            timeout_task.is_finished(),
+            "the timeout task must be aborted when the message is dropped",
+        );
+    }
+
+    #[tokio::test]
+    async fn add_chunk_does_not_retain_the_source_buffer() {
+        // `BytesDecoder` slices the read buffer without copying, so retaining it would pin
+        // the whole buffer (>= 8 KiB) per chunk.
+        let mut chunk = create_chunk(1u64, 0u8, 2u8, &"foo");
+        let source_range = chunk.as_ptr_range();
+        let mut decoder = ChunkedGelfDecoder::default();
+
+        assert!(decoder.decode_eof(&mut chunk).unwrap().is_none());
+
+        let state = decoder.state.lock().unwrap();
+        let message_state = state.values().next().expect("message pending");
+        let stored = message_state.chunks[0].as_ptr();
+        assert!(
+            !source_range.contains(&stored),
+            "the stored chunk must not alias the decoder's input buffer"
+        );
+    }
+
+    #[tokio::test]
+    async fn retrieve_message_releases_chunks_while_assembling() {
+        // Does not lower the 2x peak, just shortens how long the source side is held.
+        let mut state = MessageState::new(2, tokio::spawn(async {}));
+        state.add_chunk(0, Bytes::from_static(b"foo"));
+        state.add_chunk(1, Bytes::from_static(b"bar"));
+
+        let message = state
+            .retrieve_message()
+            .expect("message should be complete");
+
+        assert_eq!(message, Bytes::from_static(b"foobar"));
+        assert!(
+            state.chunks[..2].iter().all(Bytes::is_empty),
+            "each chunk must be released as it is copied"
+        );
+        assert_eq!(state.current_length(), 6);
+    }
+
     #[rstest]
     #[tokio::test]
     async fn decode_chunk_with_different_total_chunks() {