{"id":"CVE-2026-33246","aliases":["BIT-nats-2026-33246","GHSA-55h8-8g96-x4hj","GO-2026-4830"],"url":"https://o3.security/vulnerability/CVE-2026-33246","summary":"NATS: Leafnode connections allow spoofing of Nats-Request-Info identity headers","details":"### Background\n\nNATS.io is a high performance open source pub-sub distributed communication technology, built for the cloud, on-premise, IoT, and edge computing.\n\nThe nats-server allows hub/spoke topologies using \"leafnode\" connections by other nats-servers.  NATS messages can have headers.\n\n### Problem Description\n\nThe nats-server offers a `Nats-Request-Info:` message header, providing information about a request.  This is supposed to provide enough information to allow for account/user identification, such that NATS clients could make their own decisions on how to trust a message, provided that they trust the nats-server as a broker.\n\nA leafnode connecting to a nats-server is not fully trusted unless the system account is bridged too.  Thus identity claims should not have propagated unchecked.\n\nThus NATS clients relying upon the Nats-Request-Info: header could be spoofed.\n\nDoes not directly affect the nats-server itself, but the CVSS Confidentiality and Integrity scores are based upon what a hypothetical client might choose to do with this NATS header.\n\n### Affected Versions\n\nAny version before v2.12.6 or v2.11.15\n\n### Workarounds\n\nNone.","published":"2026-03-25T19:50:03.453Z","modified":"2026-08-12T03:51:29.242266180Z","cvss":{"score":6.4,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N"},"epss":{"score":0.00143,"percentile":0.03985,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/nats-io/nats-server/v2","fixedVersion":"2.11.15"},{"ecosystem":"Go","name":"github.com/nats-io/nats-server/v2","fixedVersion":"2.12.6"},{"ecosystem":"Go","name":"github.com/nats-io/nats-server","fixedVersion":null}],"fix":null,"references":[{"type":"ADVISORY","url":"https://advisories.nats.io/CVE/secnote-2026-08.txt"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33246.json"},{"type":"ADVISORY","url":"https://github.com/nats-io/nats-server/security/advisories/GHSA-55h8-8g96-x4hj"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33246"},{"type":"PACKAGE","url":"https://github.com/nats-io/nats-server"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:29.242266180Z"}}