CVE-2025-40923
📋 TL;DR
This vulnerability allows attackers to predict session IDs in Plack-Middleware-Session for Perl, potentially enabling session hijacking and unauthorized access to user accounts. It affects all systems using Plack-Middleware-Session versions before 0.35 with default configuration. The insecure session ID generation uses weak entropy sources unsuitable for cryptographic purposes.
💻 Affected Systems
- Plack-Middleware-Session
⚠️ 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 hijack active user sessions, gain administrative access to web applications, steal sensitive data, and perform unauthorized actions as legitimate users.
Likely Case
Attackers with some system knowledge could predict session IDs to hijack user sessions, potentially accessing user accounts and sensitive information.
If Mitigated
With proper session management controls like short session timeouts and IP validation, impact is limited to temporary account compromise.
🎯 Exploit Status
Exploitation requires understanding of the weak entropy sources and ability to predict or obtain PID and time information.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.35
Vendor Advisory: https://security.metacpan.org/docs/guides/random-data-for-security.html
Restart Required: Yes
Instructions:
1. Update Plack-Middleware-Session to version 0.35 or later using CPAN: cpanm Plack::Middleware::Session
2. Restart all Plack/PSGI applications using the middleware
3. Verify the update was successful
🔧 Temporary Workarounds
Use custom session ID generator
allImplement a custom session ID generator using cryptographically secure random number generation
Implement custom session ID generation using Crypt::URandom or similar module
🧯 If You Can't Patch
- Implement additional session validation (IP address, user-agent checking)
- Reduce session timeout duration and implement session rotation
🔍 How to Verify
Check if Vulnerable:
Check Plack-Middleware-Session version: perl -MPlack::Middleware::Session -e 'print $Plack::Middleware::Session::VERSION'Check Version:
perl -MPlack::Middleware::Session -e 'print $Plack::Middleware::Session::VERSION'Verify Fix Applied:
Verify version is 0.35 or higher and check that session IDs appear random and unpredictable📡 Detection & Monitoring
Log Indicators:
- Multiple failed session validations from same source
- Session ID reuse patterns
- Unusual session creation timestamps
Network Indicators:
- Predictable session ID patterns in HTTP requests
- Session hijacking attempts
SIEM Query:
source=web_logs (session_id matches predictable pattern) OR (multiple session_id failures from same IP)🔗 References
- https://github.com/plack/Plack-Middleware-Session/commit/1fbfbb355e34e7f4b3906f66cf958cedadd2b9be.patch
- https://github.com/plack/Plack-Middleware-Session/pull/52
- https://metacpan.org/release/MIYAGAWA/Plack-Middleware-Session-0.34/source/lib/Plack/Session/State.pm#L22
- https://security.metacpan.org/docs/guides/random-data-for-security.html
- http://www.openwall.com/lists/oss-security/2025/07/16/4
