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WalkthroughHTTP/2 stream handling now distinguishes closed or evicted streams from idle streams. Late DATA, RST_STREAM, and WINDOW_UPDATE frames are dropped. Conformance tests cover server and client behavior, flow-control credit, and early WINDOW_UPDATE frames. ChangesHTTP/2 closed-stream handling
Suggested reviewers: Priority: ⚪ Not assessed Merge Risk: 🟡 Moderate · up to Malformed frames on unopened streams can be silently accepted instead of terminating the connection with PROTOCOL_ERROR. This protocol-state defect should be fixed before merge. 🚥 Pre-merge checks | ✅ 4✅ Passed checks (4 passed)
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Updated 3:35 PM PT - Sep 12th, 2026
✅ @robobun, your commit a7d88d14286bc9179b31ffc74dd05979070ffce1 passed in 🧪 To try this PR locally: bunx bun-pr 42467That installs a local version of the PR into your bun-42467 --bun |
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Status: ready for review. The scope is narrower than at first. This PR now only drops DATA and WINDOW_UPDATE on a closed stream. The glitch rate limit and the unexpected SETTINGS ACK check that it first carried share no code with this fix and get their own PRs. Reproduced on 1.4.3-canary (6a92015):
The 6 new tests in |
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Nothing blocking. The comments below are optional suggestions. There is no need to push a fix for them before merging.
Additional findings (outside the current diff — GitHub can't attach inline comments there):
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src/runtime/api/bun/h2/connection.rs— Pre-existing sibling of the DATA-on-closed-stream fix: a WINDOW_UPDATE with a zero increment on a closed stream still writes one RST_STREAM(PROTOCOL_ERROR) and fires oneon_stream_resetJS dispatch per frame — the increment==0 branch runs before any stream lookup, so the PR's table entry "WINDOW_UPDATE on a closed stream: dropped (main)" is wrong for this case, and 100,000 such frames still yield 100,000 RSTs plus 100,000onStreamErrorcalls where node/nghttp2 send nothing. Fix: checkis_closed_stream()(or that the stream exists) before theincrement == 0stream-error branch, matching nghttp2 which resolves the stream first and returns 0 for a closed id.Extended reasoning...
Trigger: peer completes stream 1, then sends N frames of
WINDOW_UPDATE(stream=1, increment=0)(13 bytes each).wire::validate_headeraccepts them (length 4, scope Either).handle_window_updateline 897 testsincrement == 0before consultingself.streams, so line 909 writes RST_STREAM(PROTOCOL_ERROR) and line 913 callssink.on_stream_reset(1, PROTOCOL_ERROR), which inh2_frame_parser.rs:4170-4207dispatchesonStreamErrorinto JS withstream_ctx = undefined. The stream is not inself.streams, so line 910 sets nothing and the next identical frame repeats the same path — no self-limiting, no glitch charge, noinvalid_frame_countbump. nghttp2 (session_on_stream_window_update_received) callsnghttp2_session_get_stream()first; a closed id returns NULL,session_detect_idle_stream()says not-idle, and it returns 0 without RST, so node writes nothing. This is exactly the "N frames in, N RST_STREAM + N JS dispatches out" amplification the PR removes for DATA at connection.rs:1584 and 1432; the sameis_closed_stream()guard placed ahead of line 897's stream-error…Verification: pre-existing — the amplification path is real, but
handle_window_updateis byte-identical on the base branch (the diff does not touch it), so merging makes nothing worse. Mechanism,src/runtime/api/bun/h2/connection.rs: - L897if increment == 0 {runs before any stream-map lookup oris_closed_streamcheck. - L898-904: onlystream_id == 0short-circuits to a connection error. - L909…
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Confirmed, and the table row was wrong for that case. Measured with 20,000 It is the same fault as the DATA path, so I will fix it in this PR: |
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DATA on a closed stream was answered with one RST_STREAM(STREAM_CLOSED) and one JS dispatch per frame, and a zero-increment WINDOW_UPDATE with one RST_STREAM(PROTOCOL_ERROR) per frame. A client that cancelled a download sent one RST_STREAM for every DATA frame still in flight, which a node server counts against its stream reset limit. RFC 9113 5.1 has an endpoint discard frames on a closed stream after minimal processing: DATA still counts toward the connection window. nghttp2 does the same and sends nothing. A stream the embedder opened that has no engine entry yet is not closed, so its WINDOW_UPDATE still applies.
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Inline comments:
In `@src/runtime/api/bun/h2/connection.rs`:
- Line 1479: Update Connection::last_stream_id and
H2FrameParser::highest_started_stream_id to track separate local- and
peer-initiated stream high-water marks, then select the mark matching each
stream’s initiator before has_existed treats an evicted stream as closed. Ensure
handle_rst_stream, handle_data, and handle_window_update report the required
connection PROTOCOL_ERROR for idle stream 2 after peer HEADERS on stream 3, and
add a regression test covering all three frames.
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src/runtime/api/bun/h2/connection.rstest/js/node/http2/h2-conformance.test.ts
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#45801 now carries this change and its six tests. It applies one rule to HEADERS, DATA, WINDOW_UPDATE, RST_STREAM and ALTSVC on a closed stream. I close this PR in its favor. |
#46456) ### What does this PR do? Hardening for how the `node:http` and `node:http2` servers read a request: they now refuse what Node refuses. `Bun.serve` is not changed. #### `node:http` - **A request target with a byte from 0x7f to 0xff, or a control character, is answered with `400`** before any handler runs, and `'clientError'` gets `HPE_INVALID_URL`, as in Node. Bun used to run the handler with `req.url` decoded as UTF-8. No parser option relaxes this, in Node or here. - **DEL (0x7f) in a header or trailer value is answered with `400`** (`HPE_INVALID_HEADER_TOKEN`), as in Node, unless the parser is lenient (`insecureHTTPParser`, `httpValidation`, `--insecure-http-parser`). Bytes from 0x80 stay valid there and reach the handler as latin1. - **Trailers are read with the leniency the parser had.** A server made lenient through `httpValidation` or `--insecure-http-parser` lost its whole trailer section if one value had a control character. #### `node:http2` - **DATA past a request's declared `content-length` is not delivered.** The frame that crosses the length is dropped whole, and the stream is reset with `PROTOCOL_ERROR` at that frame. It used to be delivered, and the stream was reset only at the end of the request. (the request half of #45315) - Two differences from Node: Node also sends `GOAWAY` after the `RST_STREAM`, which ends the other streams of the session. This resets only the one stream, which is what RFC 9113 §8.1.1 asks for. And if the frame arrives split across reads, Node delivers the part that fits the declared length, where this delivers none of that frame. - **A space or tab at an edge of a pseudo-header's value makes the header block malformed**, as in Node: the stream is reset with `PROTOCOL_ERROR` and no user code runs. The field used to be dropped after the check that it is present, so a handler could see a request without a `:path` or a `:method`. Clients refuse it in `:status` and in a `PUSH_PROMISE` too. Without `strictFieldWhitespaceValidation`, `:protocol` may have it, as in Node. - **`:method`, `:scheme`, `:path` and `:authority` take the values nghttp2 takes.** For `http` and `https`, `:path` has to start with `/`, or be `*` with `OPTIONS`. Anything else resets the stream with `PROTOCOL_ERROR` before user code runs, in a request and in a `PUSH_PROMISE`. A `host` that isn't a valid authority is left out. - **A received field whose value has a control byte (0x01 to 0x1f except tab, or 0x7f) is left out**, as in Node, on servers and on clients: in requests, responses, 1xx blocks, trailers and pushes. Tab and bytes from 0x80 are kept. NUL, CR and LF still reset the stream. - **On a client, a response may carry only `:status`, and a `PUSH_PROMISE` may not carry it.** Anything else resets the stream with `PROTOCOL_ERROR`, as in Node. - **A request's `host` has to be non-empty and appear once**, trailers included, as in Node. Otherwise the stream is reset with `PROTOCOL_ERROR`. (#33191 covers this too) - **On a client, `:status` has to be three digits, from 100 up, and not 101**, as in Node. Otherwise the stream is reset. `"2x0"`, `"2000"`, `"+20"` and `"1e2"` used to reach `'response'` or `'headers'` as a number. (from #43498) - **DATA for a closed stream is dropped without an answer**, as in Node and as RFC 9113 §5.1 says, and the connection's flow-control window is still credited. Each such frame used to get its own `RST_STREAM(STREAM_CLOSED)`. A stream ID that was never used still gets one. (from #42467) #### Behavior change A client that sends non-ASCII bytes in the URL without escaping them gets `400` where Bun 1.4.3 answered. Measured on the wire: `curl` and Go's `net/http` do that in the query (`curl 'http://host/a?q=é'`), and Java's `HttpURLConnection`, Perl's `HTTP::Tiny`, Ruby's `Net::HTTP#get` and `http.request({ path: "/é" })` in the path and the query. Node answers all of them with `400` too. Browsers, `fetch`, `undici`, `axios`, `ws`, `wget`, Python's `requests` and `java.net.http` escape these bytes and are not affected. ### How did you verify your code works? - Every byte from 0x00 to 0xff in the path, the query, a header value, a header name and the method, sent by a raw client, on Node v26, 1.4.3, `main` and this branch, on a strict and on a lenient server. - What real clients put on the wire was captured for the clients named above. - `Bun.serve`: 4,856 raw responses are identical on `main` and on this branch. The new checks are behind `if constexpr (IsNodeHttp)`, so its instantiation of the parser doesn't contain them. - New tests in `node-http.test.ts` fail on `main` and on 1.4.3, and pass on a debug + ASAN build of this branch. - `node:http2`: 14 new tests in `h2-conformance.test.ts` (six ways of framing the body, with and without TLS, the compatibility API, and the connection's flow-control window) fail on `main` and on 1.4.3. An exact-length body, a body without `content-length` and a short body behave as before. - `node:http2` header values: 5 fields x 255 bytes x 3 positions, with `strictFieldWhitespaceValidation` on and off, sent by a raw peer. All 3,825 cells of the pseudo-headers and `host` equal Node v26. `main` differs from Node in 2,544 of the sweep's 4,590 cells. Node's own `test-http2-*` files pass (261 of 261), and the `node:http2`, `fetch` HTTP/2 and grpc-js tests give the same results as before. --------- Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com> Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>
Problem
RST_STREAM(STREAM_CLOSED)and one JS dispatch per frame (Connection::handle_datainsrc/runtime/api/bun/h2/connection.rs:None => DataDecision::Rst(ErrorCode::StreamClosed)). A zero-increment WINDOW_UPDATE getsRST_STREAM(PROTOCOL_ERROR)the same way. Node sends nothing.req.close(NGHTTP2_CANCEL)sent 4,635 RST_STREAM frames. Node counts them against its stream reset limit and ended the session. node as the client sends 1.Fix
is_closed_streamis true for aClosedentry, and for an id that was used and has no entry in either layer.handle_data,begin_streamed_dataandhandle_window_updatedrop the frame for such a stream. DATA still counts toward the connection window (RFC 9113 §5.1).handle_rst_streamuses the same id test, nowhas_existed.test/js/node/http2/h2-conformance.test.ts(6 new tests, 5 fail on main),test/js/node/http2/, and the 261test-http2-*node tests.Background
Connectionis the inbound h2 engine.H2FrameParserembeds it, still encodes outbound frames, and keeps its own stream map.Sink::is_local_streamasks that map.no_closed_streams. nghttp2 then finds no stream, skips the payload, and only updates the connection window.Notes
What node does (v26.3.0, nghttp2 1.69.0,
deps/nghttp2/lib/nghttp2_session.c)node passes
nghttp2_option_set_no_closed_streams(option, 1), songhttp2_session_get_stream_rawfinds nothing for a closed id andsession_on_data_received_fail_fastreturnsNGHTTP2_ERR_IGN_PAYLOAD.The cancel case. A stock node v26.3.0
http2.createServer()writes 100-byte messages, one per event-loop turn, behind a TCP proxy that adds 150 ms each way and counts frames. The client setsinitialWindowSizeandsetLocalWindowSizeto 1 MiB, reads for 900 ms, callsreq.close(NGHTTP2_CANCEL), then sends one more request on the same session.sessionErrorERR_HTTP2_ERROR "Protocol error"pongpongThe count per cancel is the number of DATA frames in flight. With the default 65,535-byte windows and 100-byte messages it was 330 per cancel, so a few cancels per second reach node's limit of 1,000 (refilled at 33 per second). With 16 KiB frames and the default window it is at most 4. The second CANCEL on this branch is a separate fault (the client resets the stream twice).
Floods. 20,000 one-byte DATA frames, or 20,000
WINDOW_UPDATE(increment 0)frames, on stream 1 after it was served: main writes 20,000 RST_STREAM frames back (260,120 and 260,143 bytes), node and this branch write none (120 bytes back in total). This PR does not stop the same reply for an id nobody opened. Node makes that a connection error, and #32987 covers it.WINDOW_UPDATE. A compliant peer never sends a zero increment, and a late non-zero one was already dropped. The change there is closed-state parity with nghttp2. The new part that matters is the order: nghttp2 looks the stream up before it reads the increment.
has_existedand #37985. The id test is the onehandle_rst_streamalready had: at or belowlast_stream_idor the embedder'shighest_started_stream_id(). It mixes both parities, so on a server an even id that was never used, below the highest odd id, counts as closed. #37985 addslast_peer_stream_id, a mark for peer-initiated ids only. When it lands,has_existedis the one place to switch.Scope.
Bun.serve's HTTP/2 andfetch's HTTP/2 client are separate code. They are not touched.History of this PR. It first also carried nghttp2's glitch rate limit and the unexpected SETTINGS ACK check. A self-review said to split them out because they share no code with this fix. They are #42522 (glitch rate limit) and #42519 (unexpected SETTINGS ACK) now. The WINDOW_UPDATE row comes from the review comment below.
Tests.
DATA and WINDOW_UPDATE on a closed streaminh2-conformance.test.ts, both roles, raw sockets on the other side. The server and client flood tests and the connection-window test fail on main. The last test sends WINDOW_UPDATE for a request stream before any HEADERS or DATA on it, so a 100,000-byte upload can finish. It passes on main and fails whenis_closed_streamomits theis_local_streamcheck (the upload stalls at 65,535 bytes).[human-review] gate passed · iteration 0 · 2 files touched
fails on main (without fix)
passes on PR (with fix)
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