What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-08 · updated 2026-10-09
• Weakness: CWE-405

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.

Affected products

• Golang.Org/X/Net: before 0.60.0 — fixed in 0.60.0
• Go Stdlib: before 1.26.9; from 1.27.0-0 before 1.27.2 — fixed in 1.26.9, 1.27.2
• golang.org/x/net/http2: before 0.60.0 — fixed in 0.60.0
• Go standard library net/http: before 1.26.9 — fixed in 1.26.9
• Go standard library net/http/internal/http2: from 1.27.0-0 before 1.27.2 — fixed in 1.27.2

How to fix

Upgrade to a fixed version: Golang.Org/X/Net 0.60.0; Go Stdlib 1.26.9, 1.27.2; golang.org/x/net/http2 0.60.0; Go standard library net/http 1.26.9; Go standard library net/http/internal/http2 1.27.2. Check the vendor advisory for mitigations.

References

• https://go.dev/cl/847186
• https://go.dev/cl/847308
• https://go.dev/issue/81742
• https://groups.google.com/g/golang-announce/c/U2fTuyDJznI
• https://groups.google.com/g/golang-announce/c/ZPwCyRUuGBs
• https://pkg.go.dev/vuln/GO-2026-6611

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