{"id":"GHSA-2j82-37xg-f9wp","summary":"gun has an Unexpected Status Code or Return Value vulnerability","details":"Unexpected Status Code or Return Value vulnerability in ninenines gun (gun_http module) allows a malicious HTTP server to force the client into raw protocol mode via an unsolicited 101 Switching Protocols response.\n\nIn gun_http:handle_inform/8, when a 101 Switching Protocols response is received over HTTP/1.1, the function verifies only that the Upgrade header is syntactically valid and that the stream reference is a plain reference(). It does not check whether the client ever sent an Upgrade or Connection: upgrade header on the corresponding request. Because this check is absent, any 101 response (solicited or not) causes gun to dispatch a gun_upgrade message to the caller and transition the entire connection to raw protocol mode.\n\nA malicious or compromised HTTP server can send an unsolicited 101 response to any HTTP/1.1 request, causing the gun client to abandon HTTP framing for that connection. Once in raw mode, gun_raw applies no flow control (flow=infinity) and re-arms socket active mode after every received packet, so the server can flood the client with arbitrary bytes. These are forwarded as unbounded gun_data messages to the owner process, exhausting its mailbox and BEAM memory, ultimately crashing the VM.\n\nThis issue affects gun: from 2.0.0 before 2.4.0.","aliases":["CVE-2026-43974","EEF-CVE-2026-43974"],"modified":"2026-07-29T16:11:37.119518976Z","published":"2026-06-08T15:33:00Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-07-29T15:45:59Z","nvd_published_at":"2026-06-08T15:16:46Z","cwe_ids":["CWE-841"]},"references":[{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43974"},{"type":"WEB","url":"https://github.com/ninenines/gun/commit/5b48068c29ce5e112cb149b5857c7d4dc319a81b"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-43974.html"},{"type":"PACKAGE","url":"https://github.com/ninenines/gun"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-43974"}],"affected":[{"package":{"name":"gun","ecosystem":"Hex","purl":"pkg:hex/gun"},"ranges":[{"type":"SEMVER","events":[{"introduced":"2.0.0"},{"fixed":"2.4.0"}]}],"versions":["2.0.0","2.0.1","2.1.0","2.2.0","2.3.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-2j82-37xg-f9wp/GHSA-2j82-37xg-f9wp.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}