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Vulnerabilities

Vulnerability · CVE-2026-27571

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system.

Published Feb 24, 2026 · catalog updated Jun 17, 2026 · NATS-Server is a High-Performance

Check if you run it

No confirmed exploitation is on record for CVE-2026-27571. EPSS is 0.75%. Act only if a listed version of NATS-Server is a High-Performance is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (NATS-Server is a High-Performance).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.75%
Remediation
Advisory link
Affected products
cpe linuxfoundation/nats-server

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The WebSockets handling of NATS messages handles compressed messages via the WebSockets negotiated compression. Prior to versions 2.11.2 and 2.12.3, the implementation bound the memory size of a NATS message but did not independently bound the memory consumption of the memory stream when constructing a NATS message which might then fail validation for size reasons. An attacker can use a compression bomb to cause excessive memory consumption, often resulting in the operating system terminating the server process. The use of compression is negotiated before authentication, so this does not require valid NATS credentials to exploit. The fix, present in versions 2.11.2 and 2.12.3, was to bounds the decompression to fail once the message was too large, instead of continuing on. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe linuxfoundation/nats-serverversion unspecified

How to fix CVE-2026-27571

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-27571. EPSS is 0.75%. Act only if a listed version of NATS-Server is a High-Performance is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-409; CWE-770: Allocation of Resources Without Limits or Throttling. EPSS 0.75%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 24, 2026 · NIST NVD

    Detected

    NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The WebSockets handling of NATS messages handles compressed messages via the WebSockets negotiated compression. Prior to versions 2.11.2 and 2.12.3, the implementation bound the memory size of a NATS message but did not independently bound the memory consumption of the memory stream when constructing a

  2. Jun 17, 2026 · NIST NVD

    Updated

    NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The WebSockets handling of NATS messages handles compressed messages via the WebSockets negotiated compression. Prior to versions 2.11.2 and 2.12.3, the implementation bound the memory size of a NATS message but did not independently bound the memory consumption of the memory stream when constructing a

Sources

  • CVE.orgVulnerability recordCVE-2026-27571

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-27571

    30-day exploitation probability 0.8%

    first.org
  • NIST NVDVulnerability recordCVE-2026-27571

    NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The WebSockets handling of NATS messages handles compressed messages via the WebSockets negotiated compression. Prior to versions 2.11.2 and 2.12.3, the implementation bound the memory

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.