CVE-2026-78663
Double flow control refund on HTTP/2 server streams in net/http
- State
- Published
- Severity
- 9.1 Critical
- Published
- Oct 8, 2026
- Updated
- Oct 9, 2026
- Reserved
- Aug 24, 2026
Description
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 9.1 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H | CISA-ADP |
Weaknesses
- CWE-675 Multiple Operations on Resource in Single-Operation Context
Affected Products
| Product | Versions |
|---|---|
net/httpGo standard library |
|
net/http/internal/http2Go standard library |
|
golang.org/x/net/http2golang.org/x/net |
|
References
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