Vulnerability Intelligence Report
Double flow control refund on HTTP/2 server streams in net/http
CVE-2026-78663
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.
No Active Exploit Signals
CVSS Base Score
9.1
CRITICAL
Exploitability:3.9
Impact Score:5.2
EPSS Probability:0.25%
Executive Threat Verdict
Evaluating...
Evaluating Threat Landscape...
Assessing known weaponization, exploitation telemetry, and federal advisories.
Attack Surface
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Authentication
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Weaponization
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SSVC Action
—
Weaknesses (CWE)
CWE-675 ↗CWE-675: Multiple Operations on Resource in Single-Operation Context
Affected Products & Versions
| Vendor | Product | Affected Versions |
|---|---|---|
| Go standard library | net/http | 0 < 1.26.9 (affected) |
| Go standard library | net/http/internal/http2 | 1.27.0-0 < 1.27.2 (affected) |
| golang.org/x/net | golang.org/x/net/http2 | 0 < 0.60.0 (affected) |
Threat Intelligence Signals
EPSS Score
0.248%
Identity & Timeline
| Status | PUBLISHED |
| Assigning Authority | Go Project · Vendor · USA |
| Reserved | 2026-08-24T23:36:15 |
| Published | 2026-10-08T22:53:59 |
| Last Updated | 2026-10-09T16:42:50 |
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