Cyber Resilience

CVE-2023-4649

Auth Bypass in Instantcms ≤ 2.16.1

Public PoCAuth Bypass
Published
31 August 2023
Modified
21 November 2024
Patch / advisory
View advisory
CVSS Score v3.1 5.4
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
EPSS Score 0.0037 30th percentile
Risk Priority 43 floored blend · peak EPSS

Summary

CVE-2023-4649 is a medium-severity Session Fixation (CWE-384) vulnerability in Instantcms Instantcms. Its CVSS base score is 5.4 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Steal Web Session Cookie (T1539); ranked at the 30th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

OWASP Top 10 for Web (2025)

A07:2025 Authentication Failures

EU & UK References

Vulnerability Data

Session Fixation in GitHub repository instantsoft/icms2 prior to 2.16.1.

CWE(s)
CWE-384

Related Threats

MITRE ATT&CK Enterprise Techniques

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 →
T1550.004 Web Session Cookie Lateral Movement
Adversaries can use stolen session cookies to authenticate to web applications and services.
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-2023-4654Same product: Instantcms Instantcms
CVE-2023-4187Same product: Instantcms Instantcms
CVE-2023-4653Same product: Instantcms Instantcms
CVE-2023-4189Same product: Instantcms Instantcms
CVE-2024-50348Same product: Instantcms Instantcms
CVE-2023-4652Same product: Instantcms Instantcms
CVE-2023-4879Same product: Instantcms Instantcms
CVE-2023-4655Same product: Instantcms Instantcms
CVE-2023-4381Same product: Instantcms Instantcms
CVE-2026-28281Same product: Instantcms Instantcms

Affected Assets

instantcms
instantcms
≤ 2.16.1

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

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

AC-12 Session Termination
addresses: CWE-384

Session termination after a set interval shortens the usable lifetime of a fixed session identifier, making successful exploitation of session fixation more difficult.

IA-11 Re-authentication
addresses: CWE-384

Re-authentication typically forces issuance of a new session, limiting the window for exploitation of a previously fixed session identifier.

SC-23 Session Authenticity
addresses: CWE-384

Enforces proper session ID generation and binding, preventing fixation of a known session token.

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-03 mostly match
prevents

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

PR.AA-01 partial match
prevents

Managing identities and credentials includes handling session identifiers as temporary credentials that must be invalidated on re-authentication.

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