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Apache\Web server / proxy · Chorny

CVE-2025-40931

CRITICAL · 9.1 CVSS v3.1 Published 2026-03-05
Fix available
A fix is available. Upgrade to after 1.94 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

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
Apache::Session::Generate::MD5 versions through 1.94 for Perl create insecure session id. Apache::Session::Generate::MD5 generates session ids insecurely. The default session id generator returns a MD5 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. Predicable session ids could allow an attacker to gain access to systems. Note that the libapache-session-perl package in some Debian-based Linux distributions may be patched to use Crypt::URandom.

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

The Apache::Session::Generate::MD5 Perl module generates session IDs using an insecure combination of the built-in rand() function (cryptographically weak), epoch time, and process ID. Since rand() is unsuitable for security, the PID comes from a small space, and epoch time may be guessable from HTTP headers, an attacker can predict valid session IDs and hijack user sessions.

MitigationReplace the default session ID generator with a cryptographically secure random source such as Crypt::URandom, and implement a session invalidation/migration strategy to transition existing sessions to the new secure format.

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
Apache\Web server / proxy
Affected:<= 1.94

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
None

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

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 if Apache::Session::Generate::MD5 is installed
    Run `perl -MApache::Session::Generate::MD5 -e 'print $Apache::Session::Generate::MD5::VERSION'` to check the installed version
    Affected if The module version is 1.94 or lower
  2. Locate Perl application files using Apache::Session
    Search project files for 'use Apache::Session' or 'use Apache::Session::Generate::MD5' statements, or look for session configuration files that reference this module
    Affected if The application imports or configures Apache::Session::Generate::MD5 for session handling
  3. Examine session ID generation configuration
    Review application code or configuration to determine which generator is assigned to the session store, typically in a hash passed to Apache::Session::tie() with a 'Generate' key set to Apache::Session::Generate::MD5
    Affected if The session configuration explicitly specifies Apache::Session::Generate::MD5 as the generator
  4. Inspect session ID format if accessible
    If you can obtain a session ID from the application, examine whether it follows the predictable pattern of MD5(rand output + time + PID) - however this is difficult to verify without source code review
    Affected if The application uses the default Apache::Session::Generate::MD5 for session ID generation (direct observation of ID format alone is not definitive)

If Apache::Session::Generate::MD5 version 1.94 or lower is installed and configured as the session ID generator in the application, the environment is affected by this vulnerability.

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 a release after 1.94
Interim mitigation

Replace the default session ID generator with a cryptographically secure random source such as Crypt::URandom, and implement a session invalidation/migration strategy to transition existing sessions to the new secure format.

Recommended fix High confidence

Apache::Session::Generate::MD5 version > 1.94 (e.g., 1.95 or later)

  1. Identify all Perl applications using Apache::Session::Generate::MD5 version 1.94 or earlier
  2. Stop any running services that use the affected module
  3. Install the updated version of Apache::Session::Generate::MD5 (version > 1.94) using your Perl package manager
  4. For cpanm: cpanm Apache::Session::Generate::MD5
  5. For cpan: cpan Apache::Session::Generate::MD5
  6. Verify the new version is installed: perl -MApache::Session::Generate::MD5 -e 'print $Apache::Session::Generate::MD5::VERSION'
  7. Restart affected services to load the new module
  8. If using Debian's libapache-session-perl package, ensure it includes the Crypt::URandom patch by checking: dpkg -s libapache-session-perl
Caveat Minimal risk - this module change only affects session ID generation; existing sessions should continue to work; the upgrade primarily addresses the predictability vulnerability

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

Fix this in Apache\ Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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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-2025-40931 in production — separate from our analysis above.

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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