CVE-2026-78663: critical vulnerability in Go standard library net/http
Double flow control refund on HTTP/2 server streams in net/http
Published · Updated
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28Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 9.1epss 0.6%
The HTTP/2 server can refund connection-level flow control twice for the same data: Once when a client resets a stream (refunding data for any sent-but-unread portion of the stream), and again when a request handler reads the buffered data. A malicious client can exploit this to bypass the configured connection-level flow control limit (MaxReceiveBufferPerConnection). Total buffered data is still limited by the concurrent stream limit and stream-level flow control.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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 89.5%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%