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CVE-2026-78669— Excessive CPU consumption from repeated initial window changes in net/http

Quick assessment

Affected
Go standard library net/http
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

恶意的 HTTP/2 对端可以通过打开大量数据流，并发送许多包含 SETTINGS_INITIAL_WINDOW_SIZE 值的小型 SETTINGS 帧，导致客户端或服务器出现 CPU 消耗过高的问题。

AI Predicted 5.9 Difficulty: Moderate EPSS 0.23% · P12

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 3

VendorProduct Version RangeStatus
Go standard library net/http < 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 < 0.60.0 affected
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I. Basic Information for CVE-2026-78669

Vulnerability Information
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Vulnerability Title
Excessive CPU consumption from repeated initial window changes in net/http
Source: CVE Program / CVE List V5
Vulnerability Description
A malicious HTTP/2 peer can cause excessive CPU consumption in the client or server by opening a large number of streams and then sending many small SETTINGS frames containing SETTINGS_INITIAL_WINDOW_SIZE values.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Go standard library net/http 0 ~ 1.26.9 -
Go standard library net/http/internal/http2 1.27.0-0 ~ 1.27.2 -
golang.org/x/net golang.org/x/net/http2 0 ~ 0.60.0 -

II. Public POCs for CVE-2026-78669

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-78669

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Vendor Advisories for CVE-2026-78669 (3)

Vendor Pages for CVE-2026-78669 (1)

Other References for CVE-2026-78669 (2)

Same Patch Batch · Go standard library · 2026-10-08 · 13 CVEs total

CVE-2026-94439 HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http
CVE-2026-94440 Memory limit bypass when parsing MIME headers in net/textproto, mime/multipart
CVE-2026-94448 Reset context tracking on consecutive template expressions in html/template
CVE-2026-56857 Root.Mkdir(All) can follow junctions out of the root on Windows in os
CVE-2026-56866 HTTP/1 client connection desynchronization after CONNECT rejection in net/http
CVE-2026-78659 HTTP/2 server memory exhaustion due to Trailer headers in net/http
CVE-2026-78660 HTTP/2 transport accepts malformed framing-related headers in net/http
CVE-2026-78663 Double flow control refund on HTTP/2 server streams in net/http
CVE-2026-78667 Lack of limit on size of parsed Range headers in net/http
CVE-2026-97032 HTTP/2 server crash due to HPACK encoder race in net/http
CVE-2026-97030 Recognize yield as regexp preceder keyword in html/template
CVE-2026-97031 Reject malformed ECH outer extension references in crypto/tls

IV. Related Vulnerabilities

Same product: net/http
Same vendor: Go standard library

V. Comments for CVE-2026-78669

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