# CVE-2026-78667: Go net/http denial of service in Range header parsing

Source: https://junglewise.ai/threats/cve-2026-78667-go-2026-6609-lack-of-limit-on-size-of-parsed-range-headers-in-net  
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-2026-78667 · Severity: high · CVSS 7.5 · Published 2026-10-08

Go's HTTP server implementation could consume excessive CPU when processing HTTP requests with Range headers containing many ranges. An attacker could craft a malicious Range header to cause a denial of service against web applications and services built with Go, making them unresponsive to legitimate requests.

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

## Quick answers

**Is CVE-2026-78667 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-78667 being exploited in the wild.

**How severe is CVE-2026-78667?** High severity, with a CVSS score of 7.5, published 8 October 2026.

**Which products and versions are affected?** go (Go) Go 1.27 and earlier; stdlib (Go) SEMVER:introduced=0,fixed=1.26.9,introduced=1.27.0-0,fixed=1.27.2.

**Is there a fix for CVE-2026-78667?** Yes. stdlib (Go): upgrade to 1.27.2 or later. Until then: Set GODEBUG=httpservecontentmaxranges=<limit> to configure the maximum number of allowed ranges; setting it to 0 disables the limit entirely if a workaround is needed before upgrading. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-78667 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-78667?** Check whether you run go (Go) or stdlib (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.

## How to fix

- stdlib (Go): upgrade to 1.27.2 or later

  ```sh
  go get stdlib@v1.27.2
  ```


Set GODEBUG=httpservecontentmaxranges=<limit> to configure the maximum number of allowed ranges; setting it to 0 disables the limit entirely if a workaround is needed before upgrading.

## Technical details

The net/http package's FileServer, ServeContent, and ServeFile functions lack limits on the number of ranges parsed from HTTP Range headers. An attacker can send a Range header with hundreds of small ranges to trigger excessive CPU consumption during parsing. The fix introduces a limit of 200 ranges by default, configurable via the httpservecontentmaxranges GODEBUG setting.

## Affected products

- Go Go Go 1.27 and earlier

## Identifiers

- CVE-2026-78667
- GO-2026-6609

## Timeline

- 2026-10-08: disclosed

## References

- [https://go.dev/cl/847309](https://go.dev/cl/847309)
- [https://go.dev/issue/81858](https://go.dev/issue/81858)

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