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NATS Server panic via malicious compression on leafnode port

Type: advisorySources: OSV

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.14 and 2.12.5, if the nats-server has the "leafnode" configuration enabled (not default), then anyone who can connect can crash the nats-server by triggering a panic. This happens pre-authentication and requires that compression be enabled (which it is, by default, when leafnodes are used). Versions 2.11.14 and 2.12.5 contain a fix. As a workaround, disable compression on the leafnode port.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-29785
Confirmed fixed CVEs
Not specified
Updated in this feed
5 Nov 2026, 02:09 UTC · Revision 1

Source evidence

NATS Server panic via malicious compression on leafnode port

core-osv · Original source

Published 25 Mar 2026, 19:38 UTC

NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.14 and 2.12.5, if the nats-server has the "leafnode" configuration enabled (not default), then anyone who can connect can crash the nats-server by triggering a panic. This happens pre-authentication and requires that compression be enabled (which it is, by default, when leafnodes are used). Versions 2.11.14 and 2.12.5 contain a fix. As a workaround, disable compression on the leafnode port.

osv:CVE-2026-29785
Complete source record
{
  "id": "6cfd2da9ba05f06e18e80fc76dc2e04096bd4b83a7bdec6562f03cfe7fd36c60",
  "url": "https://osv.dev/vulnerability/CVE-2026-29785",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "NATS Server panic via malicious compression on leafnode port",
    "summary": "NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Prior to versions 2.11.14 and 2.12.5, if the nats-server has the \"leafnode\" configuration enabled (not default), then anyone who can connect can crash the nats-server by triggering a panic. This happens pre-authentication and requires that compression be enabled (which it is, by default, when leafnodes are used). Versions 2.11.14 and 2.12.5 contain a fix. As a workaround, disable compression on the leafnode port.",
    "evidence": "osv:CVE-2026-29785",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-29785",
      "aliases": [
        "BIT-nats-2026-29785",
        "CVE-2026-29785",
        "GHSA-52jh-2xxh-pwh6",
        "GO-2026-4829"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/nats-io/nats-server",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "797d2514fdb29ccb2b654f7fefbcb166ccb66cf1"
                },
                {
                  "introduced": "fc6ec648d806652d282d2f0edb6cb9f22c895572"
                },
                {
                  "fixed": "0f6c831ec1df25bc3dc81d25faae0ed0bac15a96"
                },
                {
                  "fixed": "a1488de6f2ba6e666aef0f9cce0016f7f167d6a8"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "2.11.14"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "cpe": "cpe:2.3:a:linuxfoundation:nats-server:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.12.0"
                      },
                      {
                        "fixed": "2.12.5"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "a1488de6f2ba6e666aef0f9cce0016f7f167d6a8"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v2.12.4",
            "v2.11.12",
            "v2.12.5-RC.2",
            "v2.12.5-RC.1",
            "v2.11.12-RC.7",
            "v2.12.4-RC.6",
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            "v2.11.12-RC.5",
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            "v2.12.2",
            "v2.11.12-RC.4",
            "v2.12.4-RC.3",
            "v2.12.4-RC.2",
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            "v2.12.3",
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            "v2.11.11",
            "v2.12.3-RC.5",
            "v2.12.3-RC.4",
            "v2.12.3-RC.3",
            "v2.12.3-RC.2",
            "v2.12.3-RC.1",
            "v2.12.2-RC.4",
            "v2.11.11-RC.4",
            "v2.12.2-RC.3",
            "v2.11.11-RC.3",
            "v2.12.1",
            "v2.12.2-RC.2",
            "v2.11.11-RC.2",
            "v2.11.11-RC.1",
            "v2.12.2-RC.1",
            "v2.11.10",
            "v2.12.0",
            "v2.12.1-RC.5",
            "v2.12.1-RC.4",
            "v2.12.1-RC.3",
            "v2.12.1-RC.2",
            "v2.12.1-RC.1",
            "v2.11.10-RC.1",
            "v2.11.9",
            "v2.11.9-RC.3",
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            "v2.11.9-RC.1",
            "v2.11.8",
            "v2.11.8-RC.1",
            "v2.11.7",
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            "v2.11.7-RC.2",
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            "v2.11.5",
            "v2.11.5-RC.4",
            "v2.11.5-RC.3",
            "v2.11.5-RC.2",
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            "v2.11.4",
            "v2.11.4-RC.3",
            "v2.11.4-RC.2",
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            "v2.11.3",
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            "v2.11.3-RC.1",
            "v2.11.2",
            "v2.11.2-RC.3",
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            "v2.11.2-RC.1",
            "v2.11.0",
            "v2.11.0-RC.5",
            "v2.11.0-RC.4",
            "v2.11.0-RC.3",
            "v2.11.0-RC.2",
            "v2.11.0-RC.1",
            "v2.10.3",
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            "v2.10.0",
            "v2.9.22",
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            "v2.7.0-rc2",
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          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-29785.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:41.726324492Z",
      "provider": "osv",
      "references": [
        "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-29785.json",
        "https://access.redhat.com/errata/RHSA-2026:21769",
        "https://access.redhat.com/errata/RHSA-2026:22347",
        "https://access.redhat.com/errata/RHSA-2026:23345",
        "https://access.redhat.com/security/cve/CVE-2026-29785",
        "https://advisories.nats.io/CVE/secnote-2026-04.txt",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/29xxx/CVE-2026-29785.json",
        "https://github.com/nats-io/nats-server/security/advisories/GHSA-52jh-2xxh-pwh6",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-29785",
        "https://bugzilla.redhat.com/show_bug.cgi?id=2451444",
        "https://github.com/nats-io/nats-server/commit/a1488de6f2ba6e666aef0f9cce0016f7f167d6a8"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-476"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/29xxx/CVE-2026-29785.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-29785",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 509377,
  "published_at": "2026-03-25T19:38:44.587+00:00"
}