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Flagforge CVE-2025-59841

CRITICAL
Session Fixation (CWE-384)
2025-09-25 security-advisories@github.com
9.8
CVSS 3.1 · Vendor: github
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Vulnerability Assessment

Weakness
CWE
OWASP Top 10:2025
A07:2025 - Authentication Failures
ASVS 5.0
V7 - Session Management Session fixation prevention
Impact

CVSS score of 9.8 (CRITICAL). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. EPSS exploitation probability: 0.06%.

Exploit ScenarioDerived

This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the critical-severity affected system.

Act Now Prioritize within 24-48h. Why: CRITICAL severity.
Patch available 0.1% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 28, 2026

Flag Forge is a Capture The Flag (CTF) platform. Rated critical severity (CVSS 9.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified under CWE-384. Flag Forge is a Capture The Flag (CTF) platform. In versions from 2.2.0 to before 2.3.1, the FlagForge web application improperly handles session invalidation. Authenticated users can continue to access protected endpoints, such as /api/profile, even after logging out. CSRF tokens are also still valid post-logout, which can allow unauthorized actions. This issue has been patched in version 2.3.1. Affected products include: Flagforge. Version information: before 2.3.1.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (github) PRIMARY 9.8 CRITICAL
AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from Vendor (github) · only source for this CVE.

CVSS VectorVendor: github

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Patch released
Mar 28, 2026 - 19:14 nvd
Patch available
CVE Published
Sep 25, 2025 - 16:15 nvd
CRITICAL 9.8

DescriptionCVE.org

Flag Forge is a Capture The Flag (CTF) platform. In versions from 2.2.0 to before 2.3.1, the FlagForge web application improperly handles session invalidation. Authenticated users can continue to access protected endpoints, such as /api/profile, even after logging out. CSRF tokens are also still valid post-logout, which can allow unauthorized actions. This issue has been patched in version 2.3.1.

Executive ViewAI

Why It Matters

Organizations using versions from 2.2.0 to face critical risk from CVE-2025-59841 rated CVSS 9.8. Successful exploitation could critically impact the confidentiality, integrity, and availability of affected systems. A patch is available and should be applied immediately given the critical severity.

Business Impact: Severe
Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Implement network-level access controls to limit exposure; (2) Enable enhanced monitoring and alerting; (3) Apply principle of least privilege.

Threat Intelligence Overview

EPSS Score
0.1%
Top 80% exploitable
Data Quality
4 sources
Confidence: Medium

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

49
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +49
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Cross-Site Request Forgery exploits the automatic credential inclusion behavior of web browsers.

Affected Products (CPE)CVE.org

cpe:2.3:a:flagforge:flagforge:*:*:*:*:*:*:*:*

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