VulnerabilityPublished 25 Mar 2026Updated 9 Sep 2026

CVE-2026-33217: nats-server · Incorrect Authorization

Affects nats-serverSource CVE Database V5

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Not known to be exploited · CVSS 7.1 High : upgrade to 2.12.6 or 2.11.15 soon.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 3.1 base score

7.1High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 18% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.12.6, 2.11.15

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N

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

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade nats-server to 2.12.6 or 2.11.15; nats-io/nats-server to 2.11.15.

Affected software

Product	Affected	Fixed in
nats-ionats-server	Affected >=2.12.0-RC.1 <2.12.6	Fixed in 2.12.6
nats-ionats-server	Affected <2.11.15	Fixed in 2.11.15
GitHubnats-io/nats-server`pkg:github/nats-io/nats-server`Other threats	Affected <2.11.15	Fixed in 2.11.15

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in nats-server versions 2.11.15 and 2.12.6. Users should upgrade to these or later versions to remediate the vulnerability. No known workarounds or mitigations are available that meet Red Hat's criteria for ease of use and applicability. Therefore, upgrading is the recommended and effective mitigation.

Description

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 ACL checks for MQTT subjects. Versions 2.11.15 and 2.12.6 contain a fix. No known workarounds are available.

Impact

The vulnerability allows MQTT clients to bypass ACL checks, potentially leading to unauthorized disclosure of information or unauthorized modification of messages within the NATS messaging system. This can compromise confidentiality and integrity of the messaging data. There is no known impact on availability. The CVSS v3.1 score is 7.1 (High), reflecting network attack vector, low attack complexity, low privileges required, no user interaction, and high confidentiality and integrity impacts.

Summary

NATS-Server, a high-performance messaging server, had a flaw in its ACL enforcement for message subjects within the $MQTT.> namespace. Prior to versions 2.11.15 and 2.12.6, ACLs configured for message subjects were not applied correctly in this namespace, allowing MQTT clients to bypass these controls. This vulnerability could lead to unauthorized access to sensitive message subjects or unauthorized message manipulation. The vulnerability is tracked as CWE-863 (Incorrect Authorization) and CWE-425 (Direct Request 'Forced Browsing'). The issue is fixed in versions 2.11.15 and 2.12.6.

CWE-863Incorrect Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #17OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-425Direct Request (Forced Browsing) (opens in a new tab)
Base weaknessOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The web application does not adequately enforce appropriate authorization on all restricted URLs, scripts, or files.
Architecture and Design · Operation
Apply appropriate access control authorizations for each access to all restricted URLs, scripts or files.
Architecture and Design
Consider using MVC based frameworks such as Struts.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V1.2.3 (opens in a new tab)
V1.2.2 (opens in a new tab)
Attack patterns
Directory Indexing (opens in a new tab)
Detect Unpublicized Web Pages (opens in a new tab)
Detect Unpublicized Web Services (opens in a new tab)
Key Negotiation of Bluetooth Attack (KNOB) (opens in a new tab)
Forceful Browsing (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 13 Aug 2026, 16:33 UTC

WeaknessesCWE-863, CWE-425

Technical details

References

Community reviews

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