Cyber Resilience

CVE-2026-90898

Access Control

Published
14 September 2026
Modified
18 September 2026
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 0.0034 28th percentile
Risk Priority 70 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-90898 is a critical-severity Improper Access Control (CWE-284) vulnerability. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Boot or Logon Initialization Scripts (T1037); ranked at the 28th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

This vulnerability is AI-related — categorised as AI Agent Protocols and Integrations; in the Protocol-Specific Risks risk domain.

The strongest mitigations our analysis identified map to AC-14 (Permitted Actions Without Identification or Authentication) and AC-2 (Account Management) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

Bifrost registers MCP clients through its management API. A stdio client is a command plus args. Bifrost starts that program in the gateway the moment the client is added. No MCP handshake required. The default is governance.auth_config.is_enabled=false. Auth off means…

more

every caller is a local admin. One unauthenticated POST /api/mcp/client is enough to run a program as the Bifrost process user (appuser on the official image). transports/v2.1.0 refuses an unauthenticated stdio registration with 403. transports/v2.0.0 still allows it.

CWE(s)

AI Security AnalysisAI

AI Category
AI Agent Protocols and Integrations
Risk Domain
Protocol-Specific Risks
OWASP Top 10 for LLMs 2025
None mapped
Classification Reason
Matched keywords: mcp, mcp, mcp

Related Threats

MITRE ATT&CK Enterprise Techniques

T1037 Boot or Logon Initialization Scripts Persistence
Adversaries may use scripts automatically executed at boot or logon initialization to establish persistence.
T1080 Taint Shared Content Lateral Movement
T1543 Create or Modify System Process Persistence
Adversaries may create or modify system-level processes to repeatedly execute malicious payloads as part of persistence.
T1543.001 Launch Agent Persistence
Adversaries may create or modify launch agents to repeatedly execute malicious payloads as part of persistence.
T1543.003 Windows Service Persistence
Adversaries may create or modify Windows services to repeatedly execute malicious payloads as part of persistence.
T1543.004 Launch Daemon Persistence
Adversaries may create or modify Launch Daemons to execute malicious payloads as part of persistence.
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-42074Shared CWE-284, CWE-306
CVE-2025-56405Shared CWE-284, CWE-306
CVE-2026-12490Shared CWE-284, CWE-306
CVE-2026-60883Shared CWE-284, CWE-306
CVE-2026-61245Shared CWE-284, CWE-306
CVE-2026-60742Shared CWE-284, CWE-306
CVE-2026-60999Shared CWE-284, CWE-306
CVE-2026-60856Shared CWE-284, CWE-306
CVE-2026-60821Shared CWE-284, CWE-306
CVE-2026-61130Shared CWE-284, CWE-306

Affected Assets

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 14 hardening rules · 4 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V10.3.5
  • V6.2.3
  • V6.4.4
  • V10.4.16

Mitigating Controls (NIST 800-53 r5) AI

Explicitly identifies and limits actions permitted without authentication, preventing critical functions from being exposed.

Defines account types, assigns/removes access, and reviews accounts to ensure only authorized actors can reach resources.

Directly enforces approved authorizations for logical access, stopping unauthorized actors from reaching resources.

Enforces flow-control policies that restrict information movement between subjects and objects.

Documents duties and assigns access so that no single account can bypass intended restrictions.

Limits each account to the minimum privileges needed, reducing the chance of unauthorized access.

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-05 mostly match
prevents

PR.AA-05 directly enforces policy-based access management and least privilege, eliminating most improper-access-control defects, yet CWE-284 also covers implementation flaws and design gaps outside a single management control.

PR.PS-01 mostly match
prevents

Hardened baselines and deviation monitoring directly eliminate most configuration-induced access-control defects, yet CWE-284 also encompasses code-level and design flaws outside the scope of configuration management alone.

PR.PS-06 mostly match
prevents

Secure SDLC practices catch most access-control defects during design/coding/testing (mostly), yet leave residual risk from runtime configuration, architecture, and operational controls (partial).

PR.AA-01 partial match
prevents

PR.AA-01 supplies managed identities/credentials that support but do not implement access-control decisions, so it only partially prevents CWE-284 in either direction.

PR.AA-03 partial match
prevents

Authentication directly blocks unauthenticated actors (partial prevention of CWE-284) but leaves authorization logic, policy enforcement, and role checks untouched, so the control neither eliminates nor fully mitigates the broader weakness.

PR.DS-01 partial match
prevents

PR.DS-01 encryption mitigates impact of failed access checks on stored data but neither implements nor constrains access-control logic itself.

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.

prevents

High-level policy that explicitly assigns security responsibilities and mandates topic-specific rules (including access control) reduces the chance that developers or administrators will implement systems without proper authorization checks.

mitigates

The classification scheme is explicitly aligned with the access-control policy, so protective controls are applied consistently and the risk of improper access decisions is lowered.

prevents

Defining and enforcing explicit access rights and restrictions for each entity directly stops the assignment of permissions that exceed what is required, eliminating the root condition that allows improper access control.

prevents

Requiring one-to-one mapping of identities to entities and timely removal of unused identities directly stops attackers from leveraging stale or shared accounts to bypass access restrictions.

prevents

Formal authorization, role-based provisioning, and timely revocation of access rights directly stop the creation of accounts or permissions that exceed what the business actually needs.

prevents

Explicitly assigning and documenting who owns each security responsibility reduces the chance that access decisions are left undefined or inconsistently enforced.

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).

Oracle Linux 8 (4 rules)
  • V-248585 OL 8 must require reauthentication when using the "sudo" command. prevents CWE-306
  • V-248597 There must be no "shosts.equiv" files on the OL 8 operating system. prevents CWE-284
  • V-248598 There must be no ".shosts" files on the OL 8 operating system. prevents CWE-284
Oracle Linux 9 (2 rules)
  • V-271758 OL 9 file systems must not contain .shosts files. prevents CWE-284
  • V-271757 OL 9 file systems must not contain shosts.equiv files. prevents CWE-284
RHEL 7 (4 rules)
  • V-204442 The Red Hat Enterprise Linux operating system must not have the rsh-server package installed. prevents CWE-306
  • V-204606 The Red Hat Enterprise Linux operating system must not contain .shosts files. prevents CWE-284
  • V-204607 The Red Hat Enterprise Linux operating system must not contain shosts.equiv files. prevents CWE-284
RHEL 8 (4 rules)
  • V-230492 RHEL 8 must not have the rsh-server package installed. prevents CWE-306
  • V-230283 There must be no shosts.equiv files on the RHEL 8 operating system. prevents CWE-284
  • V-230284 There must be no .shosts files on the RHEL 8 operating system. prevents CWE-284

References