{"id":"CVE-2026-43972","aliases":["EEF-CVE-2026-43972","GHSA-36w4-95hv-5vwg"],"url":"https://o3.security/vulnerability/CVE-2026-43972","summary":"gun HTTP/2 PUSH_PROMISE authority not validated against connection origin allows cross-origin cookie injection","details":"Origin Validation Error vulnerability in ninenines gun (gun_http2 module) allows cross-origin cookie injection via unvalidated HTTP/2 PUSH_PROMISE authority.\n\nIn gun_http2:push_promise_frame/7, the :authority pseudo-header from an incoming PUSH_PROMISE frame is stored verbatim into the promised stream record without checking that it matches the connection's origin. When gun_http2:headers_frame/9 later processes the response headers for the promised stream, it calls gun_cookies:set_cookie_header/7 with the unvalidated server-supplied authority before any status branching and before user code can act. This violates RFC 7540 §10.6 / RFC 9113 §8.4, which require receivers to treat as a protocol error any push for a resource the server is not authoritative for.\n\nA malicious or compromised HTTP/2 server can plant cookies scoped to arbitrary third-party domains into the client's shared cookie store. This enables session fixation attacks against those domains and, if the planted cookie overrides a legitimate session token, may result in account takeover. No user interaction beyond making a normal HTTP/2 request to the attacker-controlled server is required.\n\nThis issue affects gun: from 2.0.0 before 2.4.0.","published":"2026-06-08T14:12:38.780Z","modified":"2026-08-20T03:54:18.665903660Z","cvss":null,"epss":{"score":0.00168,"percentile":0.06488,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Hex","name":"gun","fixedVersion":"2.4.0"}],"fix":{"url":"https://github.com/ninenines/gun/commit/567863ff53802fed21c3b3f25812db7f7ae29676","label":"ninenines/gun@567863f"},"references":[{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-43972"},{"type":"ADVISORY","url":"https://cna.erlef.org/cves/CVE-2026-43972.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43972.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43972"},{"type":"FIX","url":"https://github.com/ninenines/gun/commit/567863ff53802fed21c3b3f25812db7f7ae29676"},{"type":"PACKAGE","url":"https://github.com/ninenines/gun"},{"type":"PACKAGE","url":"https://github.com/ninenines/gun.git"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-20T03:54:18.665903660Z"}}