Security readout for executives and security teams
Plain-English summary
A remote, unauthenticated user can crash a vulnerable NATS server by sending a malformed WebSocket frame. The primary business risk is messaging-service downtime, not disclosed data theft or modification. Only deployments using WebSockets and exposing that port to untrusted endpoints are affected.
Executive priority
Prioritize immediate remediation for externally reachable or broadly accessible WebSocket deployments because a pre-authentication crash can interrupt messaging-dependent services. Treat isolated deployments as scheduled high-priority work after confirming network controls. Availability-sensitive environments should also verify recovery behavior and investigate recent unexplained restarts.
Technical view
NATS Server lacks a sanity check when processing a WebSocket frame length in wsRead. The resulting integer-related condition can trigger a server panic before authentication. Affected releases are 2.2.0 through 2.11.13 and 2.12.0 through 2.12.4. The CVSS 3.1 score is 7.5, reflecting high availability impact.
Likely exposure
Exposure requires WebSockets to be enabled and their network port reachable by untrusted clients. Internet-facing ports are the clearest concern, but untrusted internal clients may also qualify. Deployments without WebSockets, or with access restricted to trusted endpoints, are not described as vulnerable.
Exploitation context
The flaw is remotely reachable, requires no authentication or user interaction, and has low stated attack complexity. The supplied record is not marked as CISA KEV, and the sources provided do not establish active exploitation. Treat exposed vulnerable services as readily attackable without assuming exploitation has occurred.
Researcher notes
The supplied evidence identifies a WebSocket frame-length sanity-check failure and integer-related weaknesses, CWE-1286 and CWE-190. It does not provide evidence of confidentiality or integrity impact, active exploitation, or code execution. A workaround exists, but its precise procedure is not included here; consult the NATS advisory.
Mitigation direction
- Upgrade nats-server 2.11.x to version 2.11.14 or later.
- Upgrade nats-server 2.12.x to version 2.12.5 or later.
- Until upgraded, apply the vendor-documented workaround from the NATS advisory.
- Disable WebSockets where unnecessary or restrict the WebSocket port to trusted endpoints.
- Monitor affected servers for unexpected panics, restarts, and repeated untrusted WebSocket connections.
Validation and detection
- Inventory nats-server versions and identify deployments with WebSockets enabled.
- Confirm whether versions fall within 2.2.0–2.11.13 or 2.12.0–2.12.4.
- Map which WebSocket ports are reachable from untrusted networks or clients.
- After remediation, verify installations use 2.11.14, 2.12.5, or an applicable later fixed release.
- Review logs and uptime telemetry for unexplained panics or restarts.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-1286: 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.
Open ATT&CK lookupCWE-190: 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.
Open ATT&CK lookupCVE-2026-27889 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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.
SSVC decision data
CVSS vector scores
2 official scoresWe 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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6GitHub_MCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADPVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- ADP timelineredhat-SADP
Made public.
- CVE publishedCVE Program
The CVE record was published.
- ADP timelineredhat-SADP
Reported to Red Hat.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
- 2026-03-25T20:01:58.261Z: Reported to Red Hat.
- 2026-03-25T19:36:36.370Z: Made public.
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6CVE reference, GitHub_M · x_refsource_CONFIRM
- https://advisories.nats.io/CVE/secnote-2026-03.txtCVE reference, GitHub_M · x_refsource_MISC
- https://access.redhat.com/security/cve/CVE-2026-27889CVE reference, redhat-SADP · vdb-entry, x_refsource_REDHAT
- RHBZ#2451447CVE reference, redhat-SADP · issue-tracking, x_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27889.jsonCVE reference, redhat-SADP · x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:22347CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:23345CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:21769CVE reference, redhat-SADP · vendor-advisory, x_refsource_REDHAT
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Validation of Syntactic Correctness of Input
Improper Validation of Syntactic Correctness of Input represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.
Integer Overflow or Wraparound
Integer Overflow or Wraparound represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.