What is the CVSS score of CVE-2025-40926?

CVE-2025-40926 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.1%.

How to fix or mitigate CVE-2025-40926?

Within 24 hours: Identify all systems running Plack and document current versions in use. Within 7 days: Test and deploy the available vendor patch in a staging environment to validate compatibility with dependent applications. Within 30 days: Complete production rollout of patches across all affected systems and verify successful deployment.

Plack CVE-2025-40926

CRITICAL

Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) (CWE-338)

2026-03-05 9b29abf9-4ab0-4765-b253-1875cd9b441e

Information Disclosure Suse Plack

9.8

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-338 OWASP Top 10:2025 A04:2025 - Cryptographic Failures ASVS 5.0 V11 - Cryptography Cryptographic PRNG selection
Impact	CVSS 9.8.
Exploit ScenarioDerived	Predict session IDs.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.

Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 12, 2026

Insecure session ID generation in Plack::Middleware::Session::Simple before 0.05 for Perl. Patch available.

Earlier versions of this analysis (1)

v1 Mar 12, 2026 - 22:06 CVSS 9.8

Weak session IDs in Plack Perl middleware.

RemediationAI

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Affects your stack

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Technical ContextAI · show details

CWE-338.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 9.8 CRITICAL

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

SUSE CRITICAL

Primary rating from NVD.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Patch released

Mar 12, 2026 - 00:16 nvd

Patch available

CVE Published

Mar 05, 2026 - 02:16 nvd

CRITICAL 9.8

DescriptionCVE.org

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.

Executive ViewAI

Why It Matters

CVE-2025-40926 is a critical vulnerability in Plack that could allow attackers to gain unauthorized system access with a 9.8 CVSS severity rating. Organizations running affected Plack versions face immediate risk of compromise and should prioritize patching to prevent potential data breaches and operational disruption.

Business Impact: Severe

Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score

0.1%

Top 80% exploitable

Data Quality

4 sources

Confidence: Medium

NVD

CVE.org

EPSS Vendor

GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity CRITICAL

CISA KEV No

Public POC No

EPSS 0.1%

Patch available Yes

Active threat No

Deciding rule

CRITICAL severity

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Out-of-Cycle

Exploitation· derived

None

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact

Very High

Priority Score

Low Medium High Critical

KEV: 0

EPSS: 0

CVSS: +49

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.