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CVE-2025-40923

Plack-Middleware-Session before version 0.35 for Perl generates session ids insecurely

7.3 HighFix available

Plack-Middleware-Session before version 0.35 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.

Predicable session ids could allow an attacker to gain access to systems.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
Low

Exploit likelihood

0.39%Up 0.4 points since Jul 17, 2025
90%50%10%1%

What each source reports

CVE List Score used 7.3

Plack-Middleware-Session before version 0.35 for Perl generates session ids insecurely

Plack-Middleware-Session before version 0.35 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.

Predicable session ids could allow an attacker to gain access to systems.

Record
CVE-2025-40923
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Weakness
CWE-340, CWE-338
Updated
2026-11-02
EUVDEUVD-2025-21693 7.3

Plack-Middleware-Session before version 0.35 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.

Predicable session ids could allow an attacker to gain access to systems.

Record
EUVD-2025-21693
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Updated
2026-11-02
GitHub AdvisoriesGHSA-868p-jhqw-wrgr 7.3

Plack-Middleware-Session before version 0.35 for Perl generates session ids insecurely. The...

Plack-Middleware-Session before version 0.35 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.

Predicable session ids could allow an attacker to gain access to systems.

Record
GHSA-868p-jhqw-wrgr
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Weakness
CWE-338
Updated
2026-11-02
NVD 7.3

Plack-Middleware-Session before version 0.35 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.

Predicable session ids could allow an attacker to gain access to systems.

Record
CVE-2025-40923
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Weakness
CWE-338, CWE-340
Updated
2026-11-02
OSV 7.3

Plack-Middleware-Session before version 0.35 for Perl generates session ids insecurely

Plack-Middleware-Session before version 0.35 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.

Predicable session ids could allow an attacker to gain access to systems.

Record
CVE-2025-40923
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Weakness
CWE-338, CWE-340
Updated
2026-11-02
OSVDEBIAN-CVE-2025-40923 7.3

Plack-Middleware-Session before version 0.35 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. Predicable session ids could allow an attacker to gain access to systems.

Record
DEBIAN-CVE-2025-40923
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Updated
2026-11-02
OSVUBUNTU-CVE-2025-40923 7.3

Plack-Middleware-Session before version 0.35 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. Predicable session ids could allow an attacker to gain access to systems.

Record
UBUNTU-CVE-2025-40923
CVSS 3.1
7.3 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
libplack-middleware-session-perl
Debian:12
All versions, plus listed versions
0.33-20.34-10.36-1
None known
libplack-middleware-session-perl
Debian:13
All versions, plus listed versions
0.34-10.36-1
None known
libplack-middleware-session-perl
Debian:14
before 0.36-1, plus listed versions
0.34-1
0.36-1
libplack-middleware-session-perl
Ubuntu:16.04:LTS
All versions, plus listed versions
0.30-1
None known
libplack-middleware-session-perl
Ubuntu:18.04:LTS
All versions, plus listed versions
0.30-10.30-2
None known
libplack-middleware-session-perl
Ubuntu:20.04:LTS
All versions, plus listed versions
0.32-10.33-1
None known
libplack-middleware-session-perl
Ubuntu:22.04:LTS
All versions, plus listed versions
0.33-1
None known
libplack-middleware-session-perl
Ubuntu:24.04:LTS
All versions, plus listed versions
0.33-2
None known
libplack-middleware-session-perl
Ubuntu:25.10
All versions, plus listed versions
0.34-10.36-1
None known

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-40923 is a high vulnerability (CVSS 7.3) in Miyagawa Plack::middleware::session, published July 16, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.39%, the 33rd percentile. Fixed in libplack-middleware-session-perl 0.36-1.

References

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