# CVE-2026-78669: Go net/http excessive CPU consumption from repeated initial window changes

Source: https://junglewise.ai/threats/cve-2026-78669-go-2026-6611-excessive-cpu-consumption-from-repeated-initial  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-08. Updated: 2026-10-10  
License: CC BY 4.0 with a link back

CVE-2026-78669 · Severity: high · CVSS 7.5 · Published 2026-10-08

Go's HTTP/2 implementation in the net/http package can be forced to consume excessive CPU resources when an attacker repeatedly sends initial window size change frames. Applications using Go's HTTP server for handling network traffic may experience denial of service and become unresponsive to legitimate requests.

Technologies: [go (Go)](https://junglewise.ai/threats/technologies/go). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-78669 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-78669 being exploited in the wild.

**How severe is CVE-2026-78669?** High severity, with a CVSS score of 7.5, published 8 October 2026.

**Which products and versions are affected?** go (Go) <1.23.13, <1.22.16.

**Is there a fix for CVE-2026-78669?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-78669 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-78669?** Check whether you run go (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in Go's HTTP/2 stream window management, where repeated initial window change frames cause excessive processing overhead. An attacker can trigger this via network-accessible HTTP/2 servers without authentication. The impact is a denial-of-service condition where CPU usage becomes excessive, degrading or disabling service availability.

## Affected products

- Go Go <1.23.13, <1.22.16

## Identifiers

- CVE-2026-78669
- GO-2026-6611

## Timeline

- 2026-10-08: disclosed

## References

- [https://go.dev/cl/847186](https://go.dev/cl/847186)
- [https://go.dev/cl/847308](https://go.dev/cl/847308)

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