Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSummary
CVE-2026-27889 is a high-severity Integer Overflow or Wraparound (CWE-190) vulnerability in Linuxfoundation Nats-Server. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 45th 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 SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — 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-2026-27889 affects NATS-Server, a high-performance server for the NATS.io cloud and edge native messaging system. The vulnerability stems from a missing sanity check on WebSockets frames, which can trigger a server panic. It impacts versions starting from 2.2.0 up to but not including 2.11.14 and 2.12.5, classified under CWE-190 with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
Any unauthenticated attacker able to connect to the exposed WebSockets port can exploit this issue, as the flaw occurs before authentication. Successful exploitation causes a denial-of-service condition by crashing the server, disrupting availability without impacting confidentiality or integrity.
Patches are available in NATS-Server versions 2.11.14 and 2.12.5, with a workaround also provided. The vulnerability is limited to deployments enabling WebSockets and exposing the port to untrusted endpoints; mitigation includes restricting WebSockets usage or network access to the port as a defense-in-depth measure. Additional details are in advisories at https://advisories.nats.io/CVE/secnote-2026-03.txt and https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-15962
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation (static analysis, fuzzing, unit tests) directly finds integer overflow defects before deployment.
SI-10 requires validation of information inputs for correctness, directly stopping syntactic validation failures from being introduced or exploitable.
Secure engineering principles require use of safe arithmetic constructs or language features that structurally eliminate integer overflow during calculation.
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.
Secure SDLC practices directly require use of safe arithmetic, bounds checks, and testing that prevent integer overflows.
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 in development can detect integer overflows before release.
Secure SDLC mandates input validation and arithmetic checks that prevent integer overflows.
Application security requirements include bounds checking and safe arithmetic to avoid overflow conditions.
Secure architecture principles require defensive coding patterns that mitigate integer wraparound risks.
Secure coding standards explicitly forbid unsafe integer operations and mandate overflow-safe constructs.