CVE-2025-29993

Executive Summary

CVE-2025-29993 is an HTTP Header Injection vulnerability affecting PowerCMS. This flaw allows an attacker to inject arbitrary HTTP headers into responses generated by the application. The primary impact is the ability to manipulate email functionality, specifically to tamper with URLs in password reset emails. This can lead to account takeover if an attacker can redirect a password reset link to a malicious server. The vulnerability has a CVSS score of 5.3 (Medium), with a low EPSS score of 0.0%, indicating low exploitation activity in the wild at the time of analysis. No public proof-of-concept (PoC) code or exploit is currently available. The vendor has not released a patch, and the affected version range is unknown.

Supply Chain & Package Security

PowerCMS is a proprietary content management system. As such, it is not distributed via public package registries like NPM, PyPI, Go, or Ruby. The supply chain risk is limited to direct downloads from the vendor's official channels. Users should verify the integrity of their PowerCMS installation and monitor for official updates.

CVSS Breakdown & Threat Level

• CVSS Score: 5.3 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
• Attack Vector (AV): Network - The vulnerability can be exploited remotely.
• Attack Complexity (AC): Low - No special conditions are required.
• Privileges Required (PR): None - No authentication is needed.
• User Interaction (UI): None - The victim does not need to perform any action.
• Scope (S): Unchanged - The exploit cannot affect other components.
• Confidentiality (C): None - No data is exposed.
• Integrity (I): Low - The attacker can modify data (e.g., email content).
• Availability (A): None - The service remains available.

Threat Level: Medium. While the CVSS score is moderate, the potential for account takeover via manipulated password reset emails elevates the risk. The lack of a patch and unknown affected versions make it a significant concern for PowerCMS users.

Deep Dive & Mechanics

HTTP Header Injection (CWE-113) occurs when an application includes user-supplied input in HTTP response headers without proper sanitization. In PowerCMS, this vulnerability is specifically triggered when the application constructs email messages, particularly password reset emails.

Attack Flow:

1. An attacker identifies an input field (e.g., a parameter in a password reset request) that is reflected in the email headers.
2. The attacker injects a carriage return and line feed (%0d%0a) sequence followed by arbitrary header content.
3. The injected headers can include a Location header or modify the Content-Type to include a malicious URL.
4. When PowerCMS sends the password reset email, the injected headers cause the email client to render a tampered link.
5. The victim clicks the link, believing it is legitimate, and is redirected to an attacker-controlled server.
6. The attacker captures the reset token and completes the password reset, gaining account access.

Key Technical Details:

• The vulnerability is in the email generation component, not the web server.
• The injection point is likely in the From, Reply-To, or Subject headers, or in a custom header field.
• The attack does not require authentication, making it accessible to any remote attacker.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, the vulnerable pattern is:

Vulnerable Code (Conceptual PHP):

$headers = "From: noreply@example.com\r\n";
$headers .= "Reply-To: " . $_GET['email'] . "\r\n";
mail($to, $subject, $message, $headers);

Patched Code (Conceptual PHP):

$email = filter_var($_GET['email'], FILTER_SANITIZE_EMAIL);
$headers = "From: noreply@example.com\r\n";
$headers .= "Reply-To: " . $email . "\r\n";
mail($to, $subject, $message, $headers);

The patched version sanitizes the input using FILTER_SANITIZE_EMAIL to remove control characters and newlines.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A target PowerCMS instance (version unknown).
• An attacker-controlled SMTP server to capture email traffic (optional but recommended).
• A web server to host a malicious landing page.

Exploitation Steps:

1. Identify the password reset endpoint (e.g., /password_reset.php).
2. Craft a request with an injected header in a parameter that is reflected in the email.
3. Example HTTP request:

   POST /password_reset.php HTTP/1.1
   Host: target-powercms.com
   Content-Type: application/x-www-form-urlencoded
   
   email=attacker@evil.com%0d%0aLocation:%20http://evil.com/reset%0d%0a
   

4. The victim receives an email with a tampered reset link.
5. The victim clicks the link, sending the reset token to the attacker.
6. The attacker uses the token to reset the victim's password.

Lab Setup:

• Use a local PowerCMS installation (if available) or a vulnerable test environment.
• Set up a mail catcher like MailHog to inspect outgoing emails.
• Use Burp Suite or curl to craft and send malicious requests.

Blue Team (Defensive)

Detection:

• Monitor web server logs for unusual characters in request parameters (e.g., %0d, %0a).
• Inspect email logs for headers containing unexpected URLs or Location fields.
• Use a Web Application Firewall (WAF) to block requests with CRLF sequences.

Mitigation:

• Implement input validation and sanitization for all user-supplied data.
• Use a secure email library that automatically escapes headers.
• Apply the principle of least privilege to email sending functionality.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP requests containing %0d%0a or \r\n in parameters.
• Emails with Location headers pointing to external domains.
• Unusual From or Reply-To addresses in password reset emails.

File IOCs:

• Modified email templates in the PowerCMS installation directory.
• Suspicious log entries in /var/log/mail.log or equivalent.

Behavioral IOCs:

• Multiple password reset requests for the same user from different IPs.
• Password reset emails being sent to unexpected addresses.

Detection Engineering

YARA Rule

rule CVE_2025_29993_HTTP_Header_Injection {
    meta:
        description = "Detects HTTP header injection attempts targeting PowerCMS"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-29993"
    strings:
        $crlf = /%0[dD]%0[aA]|\\r\\n/
        $header_inject = /Location:|Content-Type:|Set-Cookie:/
    condition:
        any of ($crlf) and any of ($header_inject)
}

Sigma Rule

title: PowerCMS HTTP Header Injection Attempt
id: 8f7b3c2a-1e5d-4f9a-8c6b-0d3e7f1a2b4c
status: experimental
description: Detects HTTP requests with CRLF sequences in parameters, indicating a header injection attempt against PowerCMS.
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-query|contains:
            - '%0d%0a'
            - '%0D%0A'
            - '\r\n'
    condition: selection
falsepositives:
    - Legitimate use of encoded characters in rare cases
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-29993 PowerCMS HTTP Header Injection Attempt"; flow:to_server; content:"%0d%0a"; http_uri; nocase; content:"Location"; http_uri; nocase; distance:0; within:100; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Password Reset Functionality: Temporarily disable the password reset feature until a patch is available.
2. Input Validation: Implement strict input validation on all user-supplied data, especially in email-related parameters.
3. WAF Rules: Deploy WAF rules to block requests containing CRLF sequences (%0d%0a, \r\n).

Long-Term Fixes:

1. Vendor Patch: Apply the official patch from PowerCMS as soon as it is released.
2. Code Review: Conduct a thorough code review of the email generation module to identify and fix all injection points.
3. Use Secure Libraries: Replace custom email handling with a well-vetted library that automatically sanitizes headers (e.g., PHPMailer, SwiftMailer).

Workarounds:

• If patching is not possible, consider using a reverse proxy to filter malicious requests.
• Implement Content Security Policy (CSP) headers to mitigate the impact of injected content.

Valters IT
Securing Digital Frontiers