Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:NSummary
CVE-2026-33217 is a high-severity Incorrect Authorization (CWE-863) vulnerability in Linuxfoundation Nats-Server. Its CVSS base score is 7.1 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 18th 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-24 (Access Control Decisions) and AC-25 (Reference Monitor) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-33217 is an authorization bypass vulnerability in NATS-Server, the high-performance server implementation for NATS.io, a cloud and edge native messaging system. In versions prior to 2.11.15 and 2.12.6, Access Control Lists (ACLs) defined on message subjects are not enforced within the $MQTT.> namespace. This allows MQTT clients to evade ACL checks that would otherwise restrict access to MQTT subjects. The issue, published on 2026-03-25, is categorized under CWE-863 (Incorrect Authorization) with a CVSS v3.1 base score of 7.1 (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N).
The vulnerability can be exploited over the network by low-privileged users (PR:L) with low attack complexity and no user interaction required. An attacker leveraging an MQTT client can bypass ACL protections in the $MQTT.> namespace, enabling unauthorized publishing to or subscription from restricted MQTT subjects. This leads to a low impact on confidentiality but a high impact on integrity, potentially allowing manipulation or exposure of messaging data outside intended authorization boundaries.
NATS-Server versions 2.11.15 and 2.12.6 include fixes for this vulnerability, and upgrading to these releases is the recommended mitigation. No known workarounds exist. Additional details are available in the project advisories at https://advisories.nats.io/CVE/secnote-2026-07.txt and https://github.com/nats-io/nats-server/security/advisories/GHSA-jxxm-27vp-c3m5.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-15966
Vulnerability Data
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.15 and 2.12.6, when using ACLs on message subjects, these ACLs were not applied in the `$MQTT.>` namespace, allowing MQTT clients to bypass…
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ACL checks for MQTT subjects. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 5 hardening rules · 3 OS baselines
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Mitigating Controls (NIST 800-53 r5) AI
AC-3 directly requires correct enforcement of authorization decisions on every access request, structurally preventing incorrect checks.
AC-24 ensures access-control decisions are made and applied consistently, reducing the chance of an incorrect authorization result.
A reference monitor that is always invoked and tamper-proof forces every authorization decision through a verified, correct path.
Least-privilege assignments shrink the set of authorizations that must be checked correctly, limiting exposure to flawed checks.
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.
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.
Security testing can detect forced-browsing flaws, but the control itself does not prevent them in production.
Information access restriction implements the technical enforcement that directly blocks unauthorized direct requests.
Requiring consistency between access rights and classification plus formal approval steps ensures that the authorization logic correctly distinguishes between entities that should and should not be granted access.
Enforcing policy-driven approval and role-change reviews stops incorrect or stale authorization decisions from remaining in effect after job changes or terminations.
Privileged access rights control enforces least-privilege checks on restricted endpoints.
Secure SDLC can include authorization design, yet the control itself does not guarantee runtime enforcement.
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` (authoritative rows only; rows rated `none` are excluded).
Oracle Linux 8 (2 rules)
- V-248581 OL 8 must require users to provide a password for privilege escalation. prevents CWE-863
- V-252656 The OL 8 operating system must not be configured to bypass password requirements for privilege escalation. prevents CWE-863
RHEL 7 (1 rule)
- V-204430 The Red Hat Enterprise Linux operating system must be configured so that users must re-authenticate for privilege escalation. prevents CWE-863
RHEL 8 (1 rule)
- V-251712 The RHEL 8 operating system must not be configured to bypass password requirements for privilege escalation. prevents CWE-863