CVE-2025-40927
📋 TL;DR
CVE-2025-40927 is an HTTP response splitting vulnerability in CGI::Simple for Perl that allows attackers to inject malicious content into HTTP responses via query parameters. This can lead to reflected XSS, open redirects, cache poisoning, and header manipulation attacks. Organizations using CGI::Simple versions before 1.282 in web applications are affected.
💻 Affected Systems
- CGI::Simple
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Attackers could execute arbitrary JavaScript in users' browsers via reflected XSS, steal session cookies, redirect users to malicious sites, poison caches to serve malicious content to multiple users, and manipulate HTTP headers for various attacks.
Likely Case
Reflected XSS attacks leading to session hijacking and credential theft, or open redirects to phishing sites, especially in applications that reflect user input in HTTP headers.
If Mitigated
With proper input validation and output encoding, the risk is reduced to low, though the underlying vulnerability remains if not patched.
🎯 Exploit Status
Exploitation requires injecting newline characters (e.g., %0A) into query parameters, which is straightforward. The vulnerability is similar to well-documented HTTP response splitting attacks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.282
Vendor Advisory: https://metacpan.org/release/MANWAR/CGI-Simple-1.282
Restart Required: No
Instructions:
1. Update CGI::Simple to version 1.282 or later using CPAN: 'cpan CGI::Simple'. 2. Verify the update with 'perl -MCGI::Simple -e "print $CGI::Simple::VERSION"'. 3. Test web applications for functionality after update.
🔧 Temporary Workarounds
Input Validation and Sanitization
allImplement strict input validation to reject or sanitize newline characters (\r, \n, %0D, %0A) in query parameters before processing.
# Example Perl code to sanitize input:
my $param = $cgi->param('input');
$param =~ s/[\r\n]//g; # Remove newlines
# Use $param in HTTP headers or responses
Web Application Firewall (WAF) Rule
allConfigure WAF to block requests containing newline characters in query parameters.
# Example ModSecurity rule:
SecRule ARGS "[\r\n]" "id:1001,phase:2,deny,msg:'HTTP response splitting attempt'"
# Example nginx rule:
if ($args ~* "%0A|%0D") { return 403; }
🧯 If You Can't Patch
- Implement strict input validation in application code to filter out newline characters from all user inputs before use in HTTP responses.
- Deploy a Web Application Firewall (WAF) configured to detect and block HTTP response splitting attempts based on newline injection patterns.
🔍 How to Verify
Check if Vulnerable:
Check if CGI::Simple version is below 1.282 using: 'perl -MCGI::Simple -e "print $CGI::Simple::VERSION"'. If output is less than 1.282, the system is vulnerable.Check Version:
perl -MCGI::Simple -e "print $CGI::Simple::VERSION"Verify Fix Applied:
After patching, run the same version check command and confirm output is 1.282 or higher. Test web applications with inputs containing %0A to ensure they are properly handled.📡 Detection & Monitoring
Log Indicators:
- HTTP requests with query parameters containing %0A, %0D, \r, or \n
- Unusual HTTP response headers or multiple response headers in logs
- Errors related to malformed HTTP responses in server logs
Network Indicators:
- HTTP responses with injected headers or unexpected content
- Multiple HTTP responses from a single request indicating splitting
SIEM Query:
source="web_server_logs" AND (query="*%0A*" OR query="*%0D*" OR query="*\\r*" OR query="*\\n*")🔗 References
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2004-2320
- https://datatracker.ietf.org/doc/html/rfc7230#section-3
- https://metacpan.org/release/MANWAR/CGI-Simple-1.281/diff/MANWAR/CGI-Simple-1.282/lib/CGI/Simple.pm
- https://metacpan.org/release/MANWAR/CGI-Simple-1.281/source/lib/CGI/Simple.pm#L1031-1035
- https://owasp.org/www-community/attacks/HTTP_Response_Splitting
- https://rt.perl.org/Public/Bug/Display.html?id=21951
