{"answers":{"affected":"9 open source packages ship an affected version, including github.com/nats-io/nats-server/v2, nats and github.com/nats-io/nats-server. It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-27571 in the wild and no public exploit code.","fix":"Upgrade github.com/nats-io/nats-server/v2 to a fixed version for your release line: 2.11.12 or 2.12.3.","what":"CVE-2026-27571 is a medium-severity denial of service vulnerability in nats-io nats-server, published on 24 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-27571 and fix it if it is affected.\n\nWhat it is: CVE-2026-27571 is a medium-severity denial of service vulnerability in nats-io nats-server, published on 24 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-27571 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- github.com/nats-io/nats-server/v2 (Go): affected all versions; fixed in 2.11.12, 2.12.3\n- github.com/nats-io/nats-server/v2 (Go): affected all versions; fixed in 2.11.12\n- github.com/nats-io/nats-server/v2 (Go): affected all versions; fixed in 2.11.12\n- github.com/nats-io/nats-server/v2 (Go): affected from 2.12.0-RC.1; fixed in 2.12.3\n- github.com/nats-io/nats-server/v2 (Go): affected from 2.12.0-RC.1; fixed in 2.12.3\n- nats (Bitnami): affected all versions; fixed in 2.11.12, 2.12.3\n- github.com/nats-io/nats-server (Go): affected all versions; no fix listed\n- github.com/nats-io/nats-server (Go): affected all versions up to 1.4.1; no fix listed\n- github.com/nats-io/nats-server (Go): affected all versions up to 1.4.1; no fix listed\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-27571/ (Markdown: https://insights.sbomify.com/CVE-2026-27571/index.md)","id":"CVE-2026-27571","markdown":"https://insights.sbomify.com/CVE-2026-27571/index.md","name":"CVE-2026-27571","record":{"aliases":["AZL-78372","AZL-78374","BIT-nats-2026-27571","DEBIAN-CVE-2026-27571","ECHO-dd25-4926-4277","GHSA-qrvq-68c2-7grw","GO-2026-4533","JLSEC-2026-1120","MINI-6j34-c89h-qjfh","MINI-fffv-35fp-hf37","MINI-jx36-xwvr-6w3p","MINI-pjjw-7367-wvvc","UBUNTU-CVE-2026-27571"],"analysis":{"component_type":"server_software","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":true,"product_category":"NATS messaging server","requires_auth":"none","summary":"Unauthenticated attackers can cause a denial of service via memory exhaustion using WebSocket compression bombs in NATS server deployments.","user_interaction":"not_required","vuln_class":"denial_of_service"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[{"product":"nats-server","vendor":"linuxfoundation"}],"cvss":{"score":5.9,"severity":"medium","source":"cna","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"cwes":[{"id":"CWE-770","name":"Allocation of Resources Without Limits or Throttling"},{"id":"CWE-409","name":"Improper Handling of Highly Compressed Data (Data Amplification)"}],"description":"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.","ecosystems":["Bitnami","Go"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"nats-server websockets are vulnerable to pre-auth memory DoS","id":"CVE-2026-27571","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"Bitnami","product":null,"products":[],"type":"denial_of_service","year":"2026"},"n_packages":9,"n_references":4,"next":{"headline":"Wasmtime can panic when adding excessive fields to a `wasi:http/types.fields` instance","id":"CVE-2026-27572"},"packages":[{"ecosystem":"Bitnami","fixed":["2.11.12","2.12.3"],"introduced":["0","2.12.0"],"last_affected":[],"package":"nats","purl":"pkg:bitnami/nats","source":"BIT-nats-2026-27571"},{"ecosystem":"Go","fixed":[],"introduced":["0"],"last_affected":[],"package":"github.com/nats-io/nats-server","purl":"pkg:golang/github.com/nats-io/nats-server","source":"GO-2026-4533"},{"ecosystem":"Go","fixed":[],"introduced":["0"],"last_affected":["1.4.1"],"package":"github.com/nats-io/nats-server","purl":null,"source":"GHSA-qrvq-68c2-7grw"},{"ecosystem":"Go","fixed":[],"introduced":["0"],"last_affected":["1.4.1"],"package":"github.com/nats-io/nats-server","purl":"pkg:golang/github.com/nats-io/nats-server","source":"GHSA-qrvq-68c2-7grw"},{"ecosystem":"Go","fixed":["2.11.12","2.12.3"],"introduced":["0","2.12.0-RC.1"],"last_affected":[],"package":"github.com/nats-io/nats-server/v2","purl":"pkg:golang/github.com/nats-io/nats-server/v2","source":"GO-2026-4533"},{"ecosystem":"Go","fixed":["2.11.12"],"introduced":["0"],"last_affected":[],"package":"github.com/nats-io/nats-server/v2","purl":null,"source":"GHSA-qrvq-68c2-7grw"},{"ecosystem":"Go","fixed":["2.11.12"],"introduced":["0"],"last_affected":[],"package":"github.com/nats-io/nats-server/v2","purl":"pkg:golang/github.com/nats-io/nats-server/v2","source":"GHSA-qrvq-68c2-7grw"},{"ecosystem":"Go","fixed":["2.12.3"],"introduced":["2.12.0-RC.1"],"last_affected":[],"package":"github.com/nats-io/nats-server/v2","purl":null,"source":"GHSA-qrvq-68c2-7grw"},{"ecosystem":"Go","fixed":["2.12.3"],"introduced":["2.12.0-RC.1"],"last_affected":[],"package":"github.com/nats-io/nats-server/v2","purl":"pkg:golang/github.com/nats-io/nats-server/v2","source":"GHSA-qrvq-68c2-7grw"}],"prev":{"headline":"Discourse Vulnerable to Stored XSS via Shared AI Conversation Onebox","id":"CVE-2026-27570"},"products":["nats-server"],"published":"2026-02-24","related":[{"cvss_score":9.8,"headline":"NATS nats-server allows directory traversal via unintended path to a management action","id":"CVE-2022-28357","kev_date_added":null,"published":"2023-09-19"},{"cvss_score":8.8,"headline":"NATS Server: Route API Auth Bypass","id":"CVE-2026-58253","kev_date_added":null,"published":"2026-07-08"},{"cvss_score":8.8,"headline":"Incorrect Authorization in NATS nats-server","id":"CVE-2022-24450","kev_date_added":null,"published":"2022-02-08"},{"cvss_score":8.6,"headline":"NATS has MQTT plaintext password disclosure","id":"CVE-2026-33216","kev_date_added":null,"published":"2026-03-25"},{"cvss_score":7.7,"headline":"NATS Server: Remote crash via integer overflow in Connz pagination","id":"CVE-2026-58207","kev_date_added":null,"published":"2026-07-08"},{"cvss_score":7.5,"headline":"NATS Server: MQTT partial CONNECT packets can exhaust pre-auth memory","id":"CVE-2026-58210","kev_date_added":null,"published":"2026-07-08"},{"cvss_score":7.5,"headline":"NATS Server: Pre-auth server crash via double INFO in leafnode handshake","id":"CVE-2026-58250","kev_date_added":null,"published":"2026-07-08"}],"sources":[{"class":"attribution","licence":"Apache-2.0","name":"Bitnami","prefix":"BIT"},{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"CC BY 4.0","name":"GitHub Advisory Database","prefix":"GHSA"},{"class":"attribution","licence":"CC BY 4.0","name":"Go Vulnerability Database","prefix":"GO"},{"class":"attribution","licence":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-02-26","vendors":["nats-io"]},"summary":"Unauthenticated attackers can cause a denial of service via memory exhaustion using WebSocket compression bombs in NATS server deployments.","url":"https://insights.sbomify.com/CVE-2026-27571/"}