UnratedFix available

DEBIAN-CVE-2026-27571

Type: advisorySource: OSV1 source record

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.

Announced 24 Feb 2026Source revision 1

Original source ↗

DEBIAN-CVE-2026-27571

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:DEBIAN-CVE-2026-27571

nats-server

Source reference: /affected/0/package/name

Affected versions: 2.10.1-1
Source reference: /affected/0/versions
2.10.16-1
Source reference: /affected/0/versions
2.10.18-1
Source reference: /affected/0/versions
2.10.24-1
Source reference: /affected/0/versions
2.10.27-1
Source reference: /affected/0/versions
2.10.3-1
Source reference: /affected/0/versions
2.10.4-1
Source reference: /affected/0/versions
2.10.7-1
Source reference: /affected/0/versions
2.12.4-1
Source reference: /affected/0/versions
2.12.6-1
Source reference: /affected/0/versions
2.14.1-1
Source reference: /affected/0/versions
2.14.3-1
Source reference: /affected/0/versions
2.14.6-1
Source reference: /affected/0/versions
2.9.10-1
Source reference: /affected/0/versions
2.9.19-1
Source reference: /affected/0/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

nats-server

Source reference: /affected/1/package/name

Affected versions: 2.10.27-1
Source reference: /affected/1/versions
2.12.4-1
Source reference: /affected/1/versions
2.12.6-1
Source reference: /affected/1/versions
2.14.1-1
Source reference: /affected/1/versions
2.14.3-1
Source reference: /affected/1/versions
2.14.6-1
Source reference: /affected/1/versions
Fixed versions: Not stated in this record
Prerequisites: Not stated in this record

nats-server

Source reference: /affected/2/package/name

Affected versions: 2.10.27-1
Source reference: /affected/2/versions
Fixed versions: 2.12.4-1
Source reference: /affected/2/ranges
Prerequisites: Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          }
        ]
      }
    ],
    "package": {
      "name": "nats-server",
      "purl": "pkg:deb/debian/nats-server?arch=source&distro=bookworm",
      "ecosystem": "Debian:12"
    },
    "versions": [
      "2.10.1-1",
      "2.10.16-1",
      "2.10.18-1",
      "2.10.24-1",
      "2.10.27-1",
      "2.10.3-1",
      "2.10.4-1",
      "2.10.7-1",
      "2.12.4-1",
      "2.12.6-1",
      "2.14.1-1",
      "2.14.3-1",
      "2.14.6-1",
      "2.9.10-1",
      "2.9.19-1"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27571.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          }
        ]
      }
    ],
    "package": {
      "name": "nats-server",
      "purl": "pkg:deb/debian/nats-server?arch=source&distro=trixie",
      "ecosystem": "Debian:13"
    },
    "versions": [
      "2.10.27-1",
      "2.12.4-1",
      "2.12.6-1",
      "2.14.1-1",
      "2.14.3-1",
      "2.14.6-1"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27571.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  },
  {
    "ranges": [
      {
        "type": "ECOSYSTEM",
        "events": [
          {
            "introduced": "0"
          },
          {
            "fixed": "2.12.4-1"
          }
        ]
      }
    ],
    "package": {
      "name": "nats-server",
      "purl": "pkg:deb/debian/nats-server?arch=source&distro=forky",
      "ecosystem": "Debian:14"
    },
    "versions": [
      "2.10.27-1"
    ],
    "database_specific": {
      "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27571.json"
    },
    "ecosystem_specific": {
      "urgency": "not yet assigned"
    }
  }
]

Publisher severity

No explicit severity was provided.

Event: #56683 · Revision 1
Added to Heist Feed: Sun, 25 Oct 2026 16:46:03 GMT
Publisher date: Tue, 24 Feb 2026 17:29:03 GMT

Read the original announcement