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CVE-2026-27889 high CVSS 7.5

Vulnerability in nats (CVE-2026-27889)

Summary

Vulnerability in nats (CVE-2026-27889). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 2.11.14, 2.12.5 or later.

Original description

The description as published by the source.

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server. This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points. If one is able to do so, a defense in depth of restricting either of these will mitigate the attack.

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-27889 has been found in nats.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade nats to 2.11.14, 2.12.5 or later.
If unsure, ask your IT team or search "nats CVE-2026-27889" on the vendor's site.

CVE-2026-27889 (nats) — CWE-190 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 2.11.14, 2.12.5 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-190) exists in nats.

📍 Affected scope

Check the vendor advisory for the affected versions of nats.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 2.11.14, 2.12.5.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'nats' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'nats' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で nats を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade nats to 2.11.14, 2.12.5

    ステージング環境で 2.11.14, 2.12.5 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Bitnami nats
[{"type":"SEMVER","events":[{"introduced":"2.2.0"},{"fixed":"2.11.14"},{"introduced":"2.12.0"},{"fixed":"2.12.5"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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