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fix: ignore the reserved bit of an incoming HTTP/2 stream identifier #1261

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Merged
pjfanning merged 2 commits into from
Sep 6, 2026
Merged

fix: ignore the reserved bit of an incoming HTTP/2 stream identifier #1261

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dd20930
fix: ignore the reserved bit of an incoming HTTP/2 stream identifier
pjfanning Aug 31, 2026
8218d93
Merge branch 'main' into mask-http2-reserved-stream-id-bit
pjfanning Sep 6, 2026
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6 changes: 4 additions & 2 deletions ...re/src/main/scala/org/apache/pekko/http/impl/engine/http2/framing/Http2FrameParsing.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -193,8 +193,10 @@ private[http2] class Http2FrameParsing(
val length = reader.readShortBE() << 8 | reader.readByte()
val tpe = reader.readByte()
val flags = new ByteFlag(reader.readByte())
val streamId = reader.readIntBE()
// TODO: assert that reserved bit is 0 by checking if streamId > 0
// RFC 9113 5.1.1: the high bit of the stream identifier is reserved and MUST be ignored when receiving.
// Without masking it a peer that sets it yields a negative stream id, which never matches the stream the
// frame is really for and fails the connection instead.
val streamId = reader.readIntBE() & 0x7FFFFFFF
val payload = reader.take(length)
val maybeframe = FrameType.byId(tpe) match {
case OptionVal.Some(ft) =>
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8 changes: 8 additions & 0 deletions http2-tests/src/test/scala/org/apache/pekko/http/impl/engine/http2/Http2ServerSpec.scala
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Expand Up @@ -316,6 +316,14 @@ class Http2ServerSpec extends Http2SpecWithMaterializer("""
trailingResponseHeaders.size should be(1)
trailingResponseHeaders.head should be(("Status", "grpc-status 10"))
})
"ignore the reserved bit of a stream identifier".inAssertAllStagesStopped(
new TestSetup with RequestResponseProbes {
// RFC 9113 5.1.1: the high bit of the stream identifier is reserved and must be ignored when receiving,
// so this is a frame for stream 1 rather than one for an unusable negative stream id
network.sendHEADERS(1 | 0x80000000, endStream = true, network.headersForRequest(Get("/")))

user.expectRequest()
})
"drop a response header whose value contains CRLF".inAssertAllStagesStopped(
new TestSetup with RequestResponseProbes {
val streamId = 1
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