{"cve":"CVE-2026-78659","nvd":{"published":"2026-10-08T23:17:03.270","modified":"2026-10-09T16:35:35.900","status":"Awaiting Analysis","description":"When \"Trailer\" headers are sent by a client, the HTTP server internally uses the header values to populate the Request.Trailer map passed to the server handler. Because Request.Trailer is a map, each entry incurs memory overhead. For HTTP/2 servers, a malicious client can exploit this by sending a \"Trailer\" header that declares a large number of fields, causing the server to allocate a disproportionate amount of memory while bypassing Server.MaxHeaderValueCount and Server.MaxHeaderBytes limits. This exploit is not applicable for HTTP/1 servers, which do not support multiplexing a large number of requests over one TCP connection, and whose Server.MaxHeaderBytes are calculated differently.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-405"],"references":["https://go.dev/cl/847185","https://go.dev/cl/847314","https://go.dev/issue/81857","https://groups.google.com/g/golang-announce/c/U2fTuyDJznI","https://groups.google.com/g/golang-announce/c/ZPwCyRUuGBs"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:58:01.639778232+00:00"},"epss":{"cve":"CVE-2026-78659","score":0.00627,"percentile":0.49785,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GO-2026-6603","url":"https://osv.dev/vulnerability/GO-2026-6603","summary":"HTTP/2 server memory exhaustion due to Trailer headers in net/http","modified":"2026-10-16T09:55:47.068117441Z","packages":[{"ecosystem":"Go","name":"stdlib","purl":"pkg:golang/stdlib","ranges":["<1.26.9"],"fixed":["1.26.9"]},{"ecosystem":"Go","name":"stdlib","purl":"pkg:golang/stdlib","ranges":[">=1.27.0-0 <1.27.2"],"fixed":["1.27.2"]},{"ecosystem":"Go","name":"golang.org/x/net","purl":"pkg:golang/golang.org/x/net","ranges":["<0.60.0"],"fixed":["0.60.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}