CVE-2026-786639.1CriticalCWE-675

CVE-2026-78663: Double flow control refund on HTTP/2 server streams in net/http

Go standard library · net/http

Vendor fix available · Affected: Go standard library net/http · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.9%probability of exploitation in the next 30 days

58th percentile

050100

Higher than 58% of scored CVEs

9.1CriticalCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

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.

Affected products3

From the CVE record. A product or version that is not listed is unknown, not unaffected.

Go standard library · net/httpbefore 1.26.9
Go standard library · net/http/internal/http2from 1.27.0-0 before 1.27.2
golang.org/x/net · golang.org/x/net/http2before 0.60.0

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Multiple Operations on Resource in Single-Operation Context · Other weaknesses
Vendor: Go standard library
Published: October 2026
Band: Unlikely (under 1%), October 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-78663 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.