Cyber Resilience

CVE-2025-59841

Auth Bypass in Flagforge 2.2 – 2.3.1

Auth Bypass
Published
25 September 2025
Modified
08 October 2025
Patch / advisory
View advisory
CVSS Score v3.1 9.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0039 32th percentile
Risk Priority 71 floored blend · peak EPSS

Summary

CVE-2025-59841 is a critical-severity Session Fixation (CWE-384) vulnerability in Flagforge Flagforge. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Browser Session Hijacking (T1185); ranked at the 32th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to AC-12 (Session Termination) and SC-23 (Session Authenticity) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A07:2025 Authentication Failures

EU & UK References

Vulnerability Data

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…

more

tokens are also still valid post-logout, which can allow unauthorized actions. This issue has been patched in version 2.3.1.

CWE(s)
CWE-384CWE-613

Related Threats

MITRE ATT&CK Enterprise Techniques

T1185 Browser Session Hijacking Collection
Adversaries may take advantage of security vulnerabilities and inherent functionality in browser software to change content, modify user-behaviors, and intercept information as part of various browser session hijacking techniques.
attack.mitre.org →
T1550 Use Alternate Authentication Material Lateral Movement
Adversaries may use alternate authentication material, such as password hashes, Kerberos tickets, and application access tokens, in order to move laterally within an environment and bypass normal system access controls.
attack.mitre.org →
T1550.004 Web Session Cookie Lateral Movement
Adversaries can use stolen session cookies to authenticate to web applications and services.
attack.mitre.org →
T1563 Remote Service Session Hijacking Lateral Movement
Adversaries may take control of preexisting sessions with remote services to move laterally in an environment.
attack.mitre.org →
T1539 Steal Web Session Cookie Credential Access
An adversary may steal web application or service session cookies and use them to gain access to web applications or Internet services as an authenticated user without needing credentials.
attack.mitre.org →
T1606 Forge Web Credentials Credential Access
Adversaries may forge credential materials that can be used to gain access to web applications or Internet services.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2025-59833Same product: Flagforge Flagforge
CVE-2025-61777Same product: Flagforge Flagforge
CVE-2026-21868Same product: Flagforge Flagforge
CVE-2025-59843Same product: Flagforge Flagforge
CVE-2025-59826Same product: Flagforge Flagforge
CVE-2025-59827Same product: Flagforge Flagforge
CVE-2025-59932Same product: Flagforge Flagforge
CVE-2025-42602Shared CWE-384, CWE-613
CVE-2023-50270Shared CWE-384, CWE-613
CVE-2024-30262Shared CWE-384, CWE-613

Affected Assets

flagforge
flagforge
2.2 — 2.3.1

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V4.4.4
  • V7.6.2

Mitigating Controls (NIST 800-53 r5) AI

AC-12 Session Termination good match

AC-12 directly requires automatic session termination after a defined period, structurally preventing reuse of expired session identifiers.

SC-23 Session Authenticity good match

Requires protection of session authenticity, which directly stops an attacker from using a stolen or fixed session identifier after authentication.

AC-3 Access Enforcement partial match

Enforces that only properly authorized (i.e., freshly authenticated) sessions can access resources, making a pre-existing fixed session ID unusable.

IA-11 Re-authentication partial match

Forces re-authentication under defined conditions, which should result in issuance of a fresh session identifier and invalidation of any prior one.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.AA-01 mostly match
prevents

Credential lifecycle management directly includes enforcing session expiration to prevent reuse.

PR.AA-03 mostly match
prevents

Proper authentication processes must invalidate prior session identifiers to prevent fixation attacks.

PR.AA-05 mostly match
prevents

Authorization policy enforcement and review covers terminating stale sessions to limit access scope.

PR.AA-04 partial match
prevents

Protecting and verifying identity assertions encompasses secure handling and regeneration of session tokens.

PR.PS-01 partial match
prevents

Configuration baselines can enforce session regeneration and timeout settings that block fixation.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect session-fixation issues, yet the weakness absence does not replace comprehensive testing.

A.5.15 Access control partial match
degrades

Access-control policy can mandate session invalidation on re-authentication, but does not prescribe the technical mechanism.

A.5.16 Identity management partial match
degrades

Identity-management procedures can require new session tokens after login, yet the control is broader than session handling.

A.5.17 Authentication information partial match
degrades

Authentication-information rules can include session-token lifecycle requirements, but the control focuses on credential management.

A.8.25 Secure development life cycle partial match
prevents

Secure-SDLC requirement can embed session-fixation checks, but eliminating the weakness does not satisfy the full SDLC control.

A.8.26 Application security requirements partial match
prevents

Application-security requirements can specify session handling, yet the weakness fix alone does not meet the broader requirement.

References