Release v0.43.4

strtoul silently accepts a leading "-" and wraps via unsigned
arithmetic, so chunk-size "-2" produced ULONG_MAX-1, bypassing the
ULONG_MAX guard and letting a client drive the server toward unbounded
allocation.

Replace strtoul with a manual hex parser that requires at least one hex
digit, detects size_t overflow per digit, and accepts only chunk-ext or
end-of-line after the digits (RFC 9112 §7.1).

.github/workflows/test-32bit.yml

@@ -21,7 +21,8 @@ jobs:
       - name: Build (Win32)
         shell: cmd
         run: |
-          call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsall.bat" x86
+          for /f "usebackq tokens=*" %%i in (`"%ProgramFiles(x86)%\Microsoft Visual Studio\Installer\vswhere.exe" -latest -property installationPath`) do set VSDIR=%%i
+          call "%VSDIR%\VC\Auxiliary\Build\vcvarsall.bat" x86 || exit /b 1
           cl /std:c++14 /EHsc /W4 /WX /c /Fo:NUL test\test_32bit_build.cpp
 
   test-arm32:

.gitignore

@@ -43,6 +43,9 @@ test/test_mbedtls
 test/test_wolfssl
 test/test_no_tls
 test/server_fuzzer
+test/client_fuzzer
+test/header_parser_fuzzer
+test/url_parser_fuzzer
 test/test_proxy
 test/test_proxy_mbedtls
 test/test_proxy_wolfssl

docs-src/config.toml

@@ -4,7 +4,7 @@ langs = ["en", "ja"]
 
 [site]
 title = "cpp-httplib"
-version = "0.43.2"
+version = "0.43.4"
 hostname = "https://yhirose.github.io"
 base_path = "/cpp-httplib"
 footer_message = "© 2026 Yuji Hirose. All rights reserved."

httplib.h

@@ -8,8 +8,8 @@
 #ifndef CPPHTTPLIB_HTTPLIB_H
 #define CPPHTTPLIB_HTTPLIB_H
 
-#define CPPHTTPLIB_VERSION "0.43.2"
-#define CPPHTTPLIB_VERSION_NUM "0x002b02"
+#define CPPHTTPLIB_VERSION "0.43.4"
+#define CPPHTTPLIB_VERSION_NUM "0x002b04"
 
 #ifdef _WIN32
 #if defined(_WIN32_WINNT) && _WIN32_WINNT < 0x0A00
@@ -6361,6 +6361,10 @@ inline void get_remote_ip_and_port(socket_t sock, std::string &ip, int &port) {
   }
 }
 
+// Recursive form retained so operator""_t below can compute hashes for
+// switch-case labels at compile time (C++11 constexpr forbids loops). Do not
+// call from runtime paths with arbitrary-length inputs — use str2tag()
+// instead, which is iterative and stack-safe.
 inline constexpr unsigned int str2tag_core(const char *s, size_t l,
                                            unsigned int h) {
   return (l == 0)
@@ -6374,7 +6378,16 @@ inline constexpr unsigned int str2tag_core(const char *s, size_t l,
 }
 
 inline unsigned int str2tag(const std::string &s) {
-  return str2tag_core(s.data(), s.size(), 0);
+  // Iterative form of str2tag_core: the recursive constexpr version is kept
+  // for compile-time UDL evaluation of short string literals, but at runtime
+  // we may receive arbitrarily long inputs (e.g. fuzzed Content-Type) that
+  // would blow the stack with one frame per character.
+  unsigned int h = 0;
+  for (auto c : s) {
+    h = (((std::numeric_limits<unsigned int>::max)() >> 6) & h * 33) ^
+        static_cast<unsigned char>(c);
+  }
+  return h;
 }
 
 namespace udl {
@@ -12822,10 +12835,22 @@ inline ssize_t ChunkedDecoder::read_payload(char *buf, size_t len,
     stream_line_reader lr(strm, line_buf, sizeof(line_buf));
     if (!lr.getline()) { return -1; }
 
-    char *endptr = nullptr;
-    unsigned long chunk_len = std::strtoul(lr.ptr(), &endptr, 16);
-    if (endptr == lr.ptr()) { return -1; }
-    if (chunk_len == ULONG_MAX) { return -1; }
+    // RFC 9112 §7.1: chunk-size = 1*HEXDIG
+    const char *p = lr.ptr();
+    int v = 0;
+    if (!is_hex(*p, v)) { return -1; }
+
+    size_t chunk_len = 0;
+    constexpr size_t chunk_len_max = (std::numeric_limits<size_t>::max)();
+    for (; is_hex(*p, v); ++p) {
+      if (chunk_len > (chunk_len_max >> 4)) { return -1; }
+      chunk_len = (chunk_len << 4) | static_cast<size_t>(v);
+    }
+
+    while (is_space_or_tab(*p)) {
+      ++p;
+    }
+    if (*p != '\0' && *p != ';' && *p != '\r' && *p != '\n') { return -1; }
 
     if (chunk_len == 0) {
       chunk_remaining = 0;
@@ -12835,7 +12860,7 @@ inline ssize_t ChunkedDecoder::read_payload(char *buf, size_t len,
       return 0;
     }
 
-    chunk_remaining = static_cast<size_t>(chunk_len);
+    chunk_remaining = chunk_len;
     last_chunk_total = chunk_remaining;
     last_chunk_offset = 0;
   }
@@ -13632,7 +13657,15 @@ inline bool ClientImpl::process_request(Stream &strm, Request &req,
           output_error_log(error, &req);
           return false;
         }
-        res.body.reserve(static_cast<size_t>(len));
+        // Cap the reservation by payload_max_length_ to avoid OOM when a
+        // hostile or malformed server sends an enormous Content-Length.
+        // The actual body read below is bounded by payload_max_length_,
+        // so reserving more than that is never useful.
+        auto reserve_len = static_cast<size_t>(len);
+        if (payload_max_length_ > 0 && reserve_len > payload_max_length_) {
+          reserve_len = payload_max_length_;
+        }
+        res.body.reserve(reserve_len);
       }
     }
 

test/Makefile

@@ -18,8 +18,10 @@ ifneq ($(OS), Windows_NT)
 		OPENSSL_SUPPORT = -DCPPHTTPLIB_OPENSSL_SUPPORT -lssl -lcrypto
 		MBEDTLS_SUPPORT = -DCPPHTTPLIB_MBEDTLS_SUPPORT -lmbedtls -lmbedx509 -lmbedcrypto
 		WOLFSSL_SUPPORT = -DCPPHTTPLIB_WOLFSSL_SUPPORT -lwolfssl
-		# Disable ASLR for ASAN compatibility on WSL2 (high-entropy ASLR conflicts with ASAN shadow memory)
-		SETARCH = setarch $(shell uname -m) -R
+		ifeq ($(UNAME_S), Linux)
+			# Disable ASLR for ASAN compatibility on WSL2 (high-entropy ASLR conflicts with ASAN shadow memory)
+			SETARCH = setarch $(shell uname -m) -R
+		endif
 	endif
 endif
 
@@ -251,16 +253,38 @@ test_proxy_mbedtls : test_proxy.cc ../httplib.h Makefile cert.pem
 test_proxy_wolfssl : test_proxy.cc ../httplib.h Makefile cert.pem
 	$(CXX) -o $@ -I.. $(CXXFLAGS) test_proxy.cc $(TEST_ARGS_WOLFSSL)
 
-# Runs server_fuzzer.cc based on value of $(LIB_FUZZING_ENGINE).
-# Usage: make fuzz_test LIB_FUZZING_ENGINE=/path/to/libFuzzer
-fuzz_test: server_fuzzer
-	./server_fuzzer fuzzing/corpus/*
+# Runs all fuzz harnesses based on the value of $(LIB_FUZZING_ENGINE).
+# By default LIB_FUZZING_ENGINE is standalone_fuzz_target_runner.o, so each
+# fuzzer is replayed over its regression corpus.
+# Override for actual fuzzing:
+#   make fuzz_test LIB_FUZZING_ENGINE=/path/to/libFuzzer
+fuzz_test: server_fuzzer client_fuzzer header_parser_fuzzer url_parser_fuzzer
+	@m=""; for f in fuzzing/corpus/[0-9]* fuzzing/corpus/issue1264 fuzzing/corpus/clusterfuzz-testcase-minimized-server_fuzzer-*; do if [ -f "$$f" ]; then m="$$m $$f"; fi; done; \
+	if [ -n "$$m" ]; then echo "./server_fuzzer$$m"; ./server_fuzzer $$m; else echo "(no server_fuzzer corpus)"; fi
+	@m=""; for f in fuzzing/corpus/clusterfuzz-testcase-minimized-client_fuzzer-*; do if [ -f "$$f" ]; then m="$$m $$f"; fi; done; \
+	if [ -n "$$m" ]; then echo "./client_fuzzer$$m"; ./client_fuzzer $$m; else echo "(no client_fuzzer corpus)"; fi
+	@m=""; for f in fuzzing/corpus/clusterfuzz-testcase-minimized-header_parser_fuzzer-*; do if [ -f "$$f" ]; then m="$$m $$f"; fi; done; \
+	if [ -n "$$m" ]; then echo "./header_parser_fuzzer$$m"; ./header_parser_fuzzer $$m; else echo "(no header_parser_fuzzer corpus)"; fi
+	@m=""; for f in fuzzing/corpus/clusterfuzz-testcase-minimized-url_parser_fuzzer-*; do if [ -f "$$f" ]; then m="$$m $$f"; fi; done; \
+	if [ -n "$$m" ]; then echo "./url_parser_fuzzer$$m"; ./url_parser_fuzzer $$m; else echo "(no url_parser_fuzzer corpus)"; fi
 
 # Fuzz target, so that you can choose which $(LIB_FUZZING_ENGINE) to use.
 server_fuzzer : fuzzing/server_fuzzer.cc ../httplib.h standalone_fuzz_target_runner.o
 	$(CXX) -o $@ -I.. $(CXXFLAGS) $< $(OPENSSL_SUPPORT) $(ZLIB_SUPPORT) $(BROTLI_SUPPORT) $(LIB_FUZZING_ENGINE) $(ZSTD_SUPPORT) $(LIBS)
 	@file $@
 
+client_fuzzer : fuzzing/client_fuzzer.cc ../httplib.h standalone_fuzz_target_runner.o
+	$(CXX) -o $@ -I.. $(CXXFLAGS) $< $(OPENSSL_SUPPORT) $(ZLIB_SUPPORT) $(BROTLI_SUPPORT) $(LIB_FUZZING_ENGINE) $(ZSTD_SUPPORT) $(LIBS)
+	@file $@
+
+header_parser_fuzzer : fuzzing/header_parser_fuzzer.cc ../httplib.h standalone_fuzz_target_runner.o
+	$(CXX) -o $@ -I.. $(CXXFLAGS) $< $(OPENSSL_SUPPORT) $(ZLIB_SUPPORT) $(BROTLI_SUPPORT) $(LIB_FUZZING_ENGINE) $(ZSTD_SUPPORT) $(LIBS)
+	@file $@
+
+url_parser_fuzzer : fuzzing/url_parser_fuzzer.cc ../httplib.h standalone_fuzz_target_runner.o
+	$(CXX) -o $@ -I.. $(CXXFLAGS) $< $(OPENSSL_SUPPORT) $(ZLIB_SUPPORT) $(BROTLI_SUPPORT) $(LIB_FUZZING_ENGINE) $(ZSTD_SUPPORT) $(LIBS)
+	@file $@
+
 # Standalone fuzz runner, which just reads inputs from fuzzing/corpus/ dir and
 # feeds it to server_fuzzer.
 standalone_fuzz_target_runner.o : fuzzing/standalone_fuzz_target_runner.cpp
@@ -273,5 +297,5 @@ cert.pem:
 	./gen-certs.sh
 
 clean:
-	rm -rf test test_split test_mbedtls test_split_mbedtls test_wolfssl test_split_wolfssl test_no_tls, test_split_no_tls test_proxy test_proxy_mbedtls test_proxy_wolfssl test_benchmark server_fuzzer *.pem *.0 *.o *.1 *.srl httplib.h httplib.cc _build* *.dSYM *_shard_*.log cpp-httplib
+	rm -rf test test_split test_mbedtls test_split_mbedtls test_wolfssl test_split_wolfssl test_no_tls, test_split_no_tls test_proxy test_proxy_mbedtls test_proxy_wolfssl test_benchmark server_fuzzer client_fuzzer header_parser_fuzzer url_parser_fuzzer *.pem *.0 *.o *.1 *.srl httplib.h httplib.cc _build* *.dSYM *_shard_*.log cpp-httplib
 

test/fuzzing/corpus/clusterfuzz-testcase-minimized-client_fuzzer-5188033728282624

@@ -0,0 +1,3 @@
+ HTTP/1.1 777
+Content-Length:20000000000
+

test/fuzzing/corpus/clusterfuzz-testcase-minimized-client_fuzzer-6561074643271680

@@ -0,0 +1,3 @@
+ HTTP/1.1 777
+Content-Length:446744071854775
+

test/test.cc

@@ -5146,6 +5146,39 @@ TEST_F(ServerTest, CaseInsensitiveTransferEncoding) {
   EXPECT_EQ(StatusCode::OK_200, res->status);
 }
 
+// GHSA-h6wq-j5mv-f3q8: the server must reject malformed chunk-size lines
+// rather than treat them as valid lengths.
+template <typename ClientT>
+static void expect_chunked_body_rejected(ClientT &cli, const char *body) {
+  Request req;
+  req.method = "POST";
+  req.path = "/chunked";
+
+  std::string host_and_port;
+  host_and_port += HOST;
+  host_and_port += ":";
+  host_and_port += std::to_string(PORT);
+
+  req.headers.emplace("Host", host_and_port.c_str());
+  req.headers.emplace("Content-Length", "0");
+  req.headers.emplace("Transfer-Encoding", "chunked");
+  req.body = body;
+
+  auto res = std::make_shared<Response>();
+  auto error = Error::Success;
+  ASSERT_TRUE(cli.send(req, *res, error));
+  EXPECT_EQ(StatusCode::BadRequest_400, res->status);
+}
+
+TEST_F(ServerTest, RejectsNegativeChunkSize) {
+  expect_chunked_body_rejected(cli_, "-2\r\nAAAA\r\n0\r\n\r\n");
+}
+
+TEST_F(ServerTest, RejectsChunkSizeWithLeadingPlus) {
+  expect_chunked_body_rejected(
+      cli_, "+4\r\ndech\r\nf\r\nunked post body\r\n0\r\n\r\n");
+}
+
 TEST_F(ServerTest, GetStreamed2) {
   auto res = cli_.Get("/streamed", {{make_range_header({{2, 3}})}});
   ASSERT_TRUE(res);
@@ -9288,6 +9321,81 @@ TEST(ClientVulnerabilityTest, PayloadMaxLengthZeroMeansNoLimit) {
       << " bytes without truncation, but only read " << total_read << " bytes.";
 }
 
+// Regression test for OSS-Fuzz issue 508342856: a malicious server sending an
+// enormous Content-Length must not cause the client to pre-allocate a huge
+// response body buffer. The reservation is capped at payload_max_length_, and
+// the read itself fails when the body exceeds the limit.
+TEST(ClientVulnerabilityTest, HugeContentLengthDoesNotPreallocate) {
+#ifndef _WIN32
+  signal(SIGPIPE, SIG_IGN);
+#endif
+
+  auto server_thread = std::thread([] {
+    auto srv = ::socket(AF_INET, SOCK_STREAM, 0);
+    default_socket_options(srv);
+    detail::set_socket_opt_time(srv, SOL_SOCKET, SO_RCVTIMEO, 5, 0);
+    detail::set_socket_opt_time(srv, SOL_SOCKET, SO_SNDTIMEO, 5, 0);
+
+    sockaddr_in addr{};
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(static_cast<uint16_t>(PORT + 2));
+    ::inet_pton(AF_INET, "127.0.0.1", &addr.sin_addr);
+
+    int opt = 1;
+    ::setsockopt(srv, SOL_SOCKET, SO_REUSEADDR,
+#ifdef _WIN32
+                 reinterpret_cast<const char *>(&opt),
+#else
+                 &opt,
+#endif
+                 sizeof(opt));
+
+    ::bind(srv, reinterpret_cast<sockaddr *>(&addr), sizeof(addr));
+    ::listen(srv, 1);
+
+    sockaddr_in cli_addr{};
+    socklen_t cli_len = sizeof(cli_addr);
+    auto cli = ::accept(srv, reinterpret_cast<sockaddr *>(&cli_addr), &cli_len);
+
+    if (cli != INVALID_SOCKET) {
+      char buf[4096];
+      ::recv(cli, buf, sizeof(buf), 0);
+
+      // Malicious response: claim a 20GB body but send only a tiny payload.
+      std::string response = "HTTP/1.1 200 OK\r\n"
+                             "Content-Length: 20000000000\r\n"
+                             "\r\n"
+                             "abc";
+      ::send(cli,
+#ifdef _WIN32
+             static_cast<const char *>(response.c_str()),
+             static_cast<int>(response.size()),
+#else
+             response.c_str(), response.size(),
+#endif
+             0);
+
+      detail::close_socket(cli);
+    }
+    detail::close_socket(srv);
+  });
+
+  std::this_thread::sleep_for(std::chrono::milliseconds(200));
+
+  {
+    Client cli("127.0.0.1", PORT + 2);
+    cli.set_read_timeout(5, 0);
+    // Default payload_max_length_ is 100MB; a 20GB Content-Length must not
+    // result in a 20GB pre-allocation. The Get() call is expected to fail
+    // (server claims more bytes than payload_max_length permits), but it must
+    // not exhaust memory before getting there.
+    auto res = cli.Get("/malicious");
+    EXPECT_FALSE(res); // Read fails because body exceeds payload_max_length_
+  }
+
+  server_thread.join();
+}
+
 // Verify that content_receiver bypasses the default payload_max_length,
 // allowing streaming downloads larger than 100MB without requiring an explicit
 // set_payload_max_length call.

test/test_proxy.cc

@@ -291,10 +291,12 @@ template <typename T> void KeepAliveTest(T &cli, bool basic) {
 
   {
     auto res = cli.Get("/get");
+    ASSERT_TRUE(res != nullptr);
     EXPECT_EQ(StatusCode::OK_200, res->status);
   }
   {
     auto res = cli.Get("/redirect/2");
+    ASSERT_TRUE(res != nullptr);
     EXPECT_EQ(StatusCode::OK_200, res->status);
   }
 
@@ -306,6 +308,7 @@ template <typename T> void KeepAliveTest(T &cli, bool basic) {
 
     for (auto path : paths) {
       auto res = cli.Get(path.c_str());
+      ASSERT_TRUE(res != nullptr);
       auto body = normalizeJson(res->body);
       EXPECT_TRUE(body.find("\"authenticated\":true") != std::string::npos);
       EXPECT_TRUE(body.find("\"user\":\"hello\"") != std::string::npos);
@@ -317,6 +320,7 @@ template <typename T> void KeepAliveTest(T &cli, bool basic) {
     int count = 10;
     while (count--) {
       auto res = cli.Get("/get");
+      ASSERT_TRUE(res != nullptr);
       EXPECT_EQ(StatusCode::OK_200, res->status);
     }
   }