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CVE Record

CVE-2026-33216: NATS has MQTT plaintext password disclosure

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, for MQTT deployments using usercodes/passwords: MQTT passwords are incorrectly classified as a non-authenticating identity statement (JWT) and exposed via monitoring endpoints. Versions 2.11.14 and 2.12.6 contain a fix. As a workaround, ensure monitoring end-points are adequately secured. Best practice remains to not expose the monitoring endpoint to the Internet or other untrusted network users.

HighCVSS 8.6Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Affected NATS servers can reveal MQTT user passwords through monitoring endpoints. An attacker who can reach those endpoints may obtain credentials without authenticating, creating a serious confidentiality and account-compromise risk. Exposure requires MQTT username/password authentication and accessible monitoring endpoints.

Executive priority

Treat as urgent where MQTT password authentication and exposed monitoring coexist. Prioritize immediate endpoint isolation, then upgrade and credential rotation. Lower priority may be justified only after confirming monitoring is inaccessible to untrusted users or the affected MQTT configuration is absent.

Technical view

NATS incorrectly treats MQTT passwords as non-authenticating JWT identity data, causing plaintext passwords to appear in monitoring output. The stated affected ranges are below 2.11.15 and 2.12.0-RC.1 through 2.12.5. CVSS 3.1 is 8.6, reflecting unauthenticated network access and high confidentiality impact without direct integrity or availability impact.

Likely exposure

Highest risk applies to affected NATS versions using MQTT usercodes/passwords where monitoring endpoints are reachable from the Internet or untrusted networks. Deployments not using MQTT password authentication, or with monitoring strictly restricted to trusted administrators, have substantially lower exposure to this flaw.

Exploitation context

The bundle reports no CISA KEV listing and provides no evidence of active exploitation. Exploitation would require network access to an affected monitoring endpoint; no prior privileges or user interaction are indicated by the CVSS vector.

Researcher notes

The source bundle is internally inconsistent: its affected range includes 2.11.14, while its description also calls 2.11.14 fixed. Confirm the correct 2.11 remediation release with the NATS advisory. The evidence supports credential disclosure, but not demonstrated credential reuse, downstream compromise, or active exploitation.

Mitigation direction

  • Upgrade to a release outside the stated affected ranges, subject to vendor confirmation.
  • Use 2.12.6 or later for the 2.12 branch.
  • Restrict monitoring endpoints to trusted administrative networks and authenticated operators.
  • Rotate exposed MQTT passwords if monitoring access by untrusted parties cannot be ruled out.
  • Review the NATS advisory before selecting a 2.11 branch target because the supplied version statements conflict.

Validation and detection

  • Inventory NATS versions and identify deployments using MQTT username/password authentication.
  • Confirm monitoring endpoints are not reachable from the Internet or untrusted network segments.
  • Review monitoring access logs for unexpected clients during the vulnerable period.
  • Verify upgraded instances report a vendor-confirmed unaffected version.
  • Check monitoring responses safely to confirm MQTT passwords are no longer disclosed.
Prepared
Confidence
high
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-213: Exact CWE lookup

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cwe · low confidence lookup

CWE-256: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

Credential and access behavior lookup

The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2026-33216 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.6 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
10Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.6CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N3.94GitHub_M
8.6CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N3.94redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

8.6High
CVSS 3.1 vector shape for CVE-2026-33216Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPnats-server: github.com/nats-io/nats-server: NATS-Server: Information disclosure of MQTT passwords through monitoring endpoints
other:Red Hat severity ratingcvssV3_1
  • 2026-03-25T20:02:03.000Z: Reported to Red Hat.
  • 2026-03-25T19:41:55.670Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
nats-ionats-server< 2.11.15, >= 2.12.0-RC.1, < 2.12.6Listed
Weakness

CWE details

CWE-213CWE-256

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-213 · source CWE mapping

Exposure of Sensitive Information Due to Incompatible Policies

Exposure of Sensitive Information Due to Incompatible Policies represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-256 · source CWE mapping

Plaintext Storage of a Password

Plaintext Storage of a Password represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs