CVE-2026-78659: high-severity vulnerability in Go standard library net/http
HTTP/2 server memory exhaustion due to Trailer headers in net/http
Published · Updated
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21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.6%
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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products
golang.org/x/net · golang.org/x/net/http2Go standard library · net/httpGo standard library · net/http/internal/http2Related CVEs — Go standard library net/http
In the same product, most dangerous first.
CVE-2023-45288HIGHHTTP/2 CONTINUATION flood in net/httpEPSS 92.0%CVE-2022-41717—Excessive memory growth in net/http and golang.org/x/net/http2EPSS 6.1%CVE-2022-41723HIGHDenial of service via crafted HTTP/2 stream in net/http and golang.org/x/netEPSS 4.6%CVE-2023-39325—HTTP/2 rapid reset can cause excessive work in net/httpEPSS 3.8%CVE-2026-39821CRITICALInvoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idnaEPSS 1.8%CVE-2022-1705MEDIUMImproper sanitization of Transfer-Encoding headers in net/httpEPSS 1.5%