dbcve.org
Plack\Application · Kazeburo

CVE-2025-40926

CRITICAL · 9.8 CVSS v3.1 Published 2026-03-05
Fix available
A fix is available. Upgrade to 0.05 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Plack::Middleware::Session::Simple versions before 0.05 for Perl generates session ids insecurely. The default session id generator returns a SHA-1 hash seeded with the built-in rand function, the epoch time, and the PID. The PID will come from a small set of numbers, and the epoch time may be guessed, if it is not leaked from the HTTP Date header. The built-in rand function is unsuitable for cryptographic usage. Predictable session ids could allow an attacker to gain access to systems. Plack::Middleware::Session::Simple is intended to be compatible with Plack::Middleware::Session, which had a similar security issue CVE-2025-40923.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Plack::Middleware::Session::Simple before version 0.05 uses a weak session ID generator combining SHA-1 hashing with insecure entropy sources: the non-cryptographic Perl rand() function, epoch time, and a small-range PID. Since PIDs come from a limited set and epoch time can be guessed (potentially leaked via HTTP Date headers), session IDs are predictable, enabling session hijacking attacks.

MitigationUpgrade Plack::Middleware::Session::Simple to version 0.05 or later which uses a cryptographically secure random number generator for session ID generation, and verify existing session functionality continues to work correctly.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Plack\Application
Affected:< 0.05

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Plack::Middleware::Session::Simple version
    Run 'perl -MPlack::Middleware::Session::Simple -e 'print $Plack::Middleware::Session::Simple::VERSION' in the application environment
    Affected if Version returned is absent or less than 0.05 (e.g., 0.04, 0.03, etc.)
  2. Confirm Plack middleware usage
    Inspect your Plack application configuration (e.g., app.psgi, startup script) for 'Plack::Middleware::Session::Simple' in the middleware stack
    Affected if The middleware is loaded and used for session handling
  3. Check session ID format if accessible
    If you can inspect a generated session cookie, examine the session ID pattern; weak IDs may contain predictable timestamp or PID patterns in the first bytes
    Affected if Session IDs appear to contain epoch time or low-range numeric patterns that repeat across regenerations

If the installed Plack::Middleware::Session::Simple version is below 0.05 and your application uses this middleware for sessions, session IDs are predictable and vulnerable to hijacking.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.05 or later
Fixed in 0.05
Vendor patch github.com →
Interim mitigation

Upgrade Plack::Middleware::Session::Simple to version 0.05 or later which uses a cryptographically secure random number generator for session ID generation, and verify existing session functionality continues to work correctly.

Recommended fix High confidence

0.05

  1. Check current version of Plack::Middleware::Session::Simple by running: cpan -D Plack::Middleware::Session::Simple or perldoc -v Plack::Middleware::Session::Simple
  2. Upgrade to version 0.05 or later using: cpanm Plack::Middleware::Session::Simple or cpan Plack::Middleware::Session::Simple
  3. Verify the upgrade was successful by checking the installed version: cpan -D Plack::Middleware::Session::Simple
  4. Restart any Perl/Plack applications that use this module to ensure they load the new version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Plack\ Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,920
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,072.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2025-40926 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-40926 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data