CVE-2023-29406: Insufficient sanitization of Host header in net/http

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-07-11 · updated 2026-06-17
Weakness: CWE-436

Description

The HTTP/1 client does not fully validate the contents of the Host header. A maliciously crafted Host header can inject additional headers or entire requests. With fix, the HTTP/1 client now refuses to send requests containing an invalid Request.Host or Request.URL.Host value.

Affected products

Go: before 1.19.11; from 1.20.0 before 1.20.6 — fixed in 1.19.11, 1.20.6

How to fix

Upgrade to a fixed version: Go 1.19.11, 1.20.6. Check the vendor advisory for mitigations.

References

https://go.dev/cl/506996
https://go.dev/issue/60374
https://groups.google.com/g/golang-announce/c/2q13H6LEEx0
https://pkg.go.dev/vuln/GO-2023-1878
https://security.gentoo.org/glsa/202311-09
https://security.netapp.com/advisory/ntap-20230814-0002/
https://go.dev/cl/506996
https://go.dev/issue/60374
https://groups.google.com/g/golang-announce/c/2q13H6LEEx0
https://pkg.go.dev/vuln/GO-2023-1878
https://security.gentoo.org/glsa/202311-09
https://security.netapp.com/advisory/ntap-20230814-0002/

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