Fix Host header not being modified by RequestHeaderModifier by mihuross · Pull Request #12805 · traefik/traefik

mihuross · 2026-03-13T06:51:14Z

What does this PR do?

In Go's net/http, setting the Host header via req.Header.Set is a no-op. The Host header must be set directly on req.Host, similar to what is already done in the customRequestHeaders middleware.

Motivation

Fixes #12793

More

Added/updated tests
Added/updated documentation

To my understanding this does not need extra doc, because it is more of fix than extra feature.

kevinpollet · 2026-03-16T13:37:44Z

Hey @mihuross ,

Thanks for this contribution!

We've set this to "review" and will take a look at the code.
We'll update you once the review is done.

Could you please rebase this pull request on branch v3.6 as this is a fix?

mihuross · 2026-03-16T13:40:35Z

Could you please rebase this pull request on branch v3.6 as this is a fix?

sure, I was at the impression that this has been there from the start for few years already, so it is not something that should be merged as hot bug.

mihuross · 2026-04-13T06:23:20Z

@mmatur any else that needs to be done from side?

nmengin · 2026-04-13T12:34:51Z

Hey @mihuross,

Thanks for reaching out! This is definitely on our radar.
We're focused on other priorities right now though, and we don't have an ETA yet—even though we plan to get to it.
We'll keep you updated as soon as we can move forward!

kevinpollet

Thanks 👍

rtribotte

Thanks!

…HeaderModifier In Go's net/http, setting the Host header via req.Header.Set is a no-op. The Host header must be set directly on req.Host, similar to what is already done in the customRequestHeaders middleware.

traefiker · 2026-06-18T09:50:12Z

🚫 the mergeable state is "blocked"

This PR contains the following updates: | Package | Update | Change | |---|---|---| | [traefik](https://github.com/containous/traefik) | patch | `v3.7.5` → `v3.7.6` | --- > ⚠️ **Warning** > > Some dependencies could not be looked up. Check the [Dependency Dashboard](issues/12) for more information. --- ### Release Notes <details> <summary>containous/traefik (traefik)</summary> ### [`v3.7.6`](https://github.com/containous/traefik/blob/HEAD/CHANGELOG.md#v376-2026-06-30) [Compare Source](traefik/traefik@v3.7.6...v3.7.6) [All Commits](traefik/traefik@v3.7.5...v3.7.6) **Bug fixes:** - **\[acme, logs]** Bump github.com/go-acme/lego/v5 ([#13154](traefik/traefik#13154) [@ldez](https://github.com/ldez)) - **\[acme]** Bump github.com/go-acme/lego/v5 ([#13359](traefik/traefik#13359) [@juliens](https://github.com/juliens)) - **\[k8s, k8s/ingress-nginx]** Fix ingress-nginx ssl passthrough status updates ([#13212](traefik/traefik#13212) [@nickmnt](https://github.com/nickmnt)) - **\[k8s/gatewayapi]** Add missing Gateway API features in conformance tests ([#13356](traefik/traefik#13356) [@AnatoleLucet](https://github.com/AnatoleLucet)) - **\[k8s/gatewayapi]** Avoid collisions for Gateway API services names ([#13367](traefik/traefik#13367) [@rtribotte](https://github.com/rtribotte)) - **\[k8s/gatewayapi]** Ignore other gateways parentRefs and update route parent statuses only for managed gateways ([#13397](traefik/traefik#13397) [@rtribotte](https://github.com/rtribotte)) - **\[k8s/ingress-nginx]** Configure retry according to buffering configuration ([#13039](traefik/traefik#13039) [@rtribotte](https://github.com/rtribotte)) - **\[k8s/ingress-nginx]** Fix force-ssl-redirect routing 418 when TLS is terminated upstream ([#13386](traefik/traefik#13386) [@carloslima](https://github.com/carloslima)) - **\[k8s]** Detect EndpointSlice condition changes ([#13405](traefik/traefik#13405) [@kevinpollet](https://github.com/kevinpollet)) - **\[k8s]** Index Kubernetes EndpointSlice by service name ([#13395](traefik/traefik#13395) [@kevinpollet](https://github.com/kevinpollet)) - **\[k8s]** Sort endpointslices to keep backend IPs consistent across rebuilds ([#13406](traefik/traefik#13406) [@kevinpollet](https://github.com/kevinpollet)) - **\[kv]** Bump kvtools/redis to v1.2.1 ([#13403](traefik/traefik#13403) [@ldez](https://github.com/ldez)) - **\[middleware, authentication]** Fix x-forwarded-port in forward-auth ([#13344](traefik/traefik#13344) [@juliens](https://github.com/juliens)) - **\[middleware, k8s/gatewayapi]** Fix Gateway API redirect missing statuses ([#13360](traefik/traefik#13360) [@AnatoleLucet](https://github.com/AnatoleLucet)) - **\[middleware, k8s/gatewayapi]** Fix Host header not being modified by RequestHeaderModifier ([#12805](traefik/traefik#12805) [@mihuross](https://github.com/mihuross)) - **\[middleware, k8s/gatewayapi]** Fix request scheme derivation when Gateway API RequestRedirect omits scheme ([#13347](traefik/traefik#13347) [@gndz07](https://github.com/gndz07)) - **\[middleware]** Fix CORS Max-Age set to 0 by default ([#13371](traefik/traefik#13371) [@AnatoleLucet](https://github.com/AnatoleLucet)) - **\[middleware]** Fix CORS wildcard when allow-credentials is true ([#13368](traefik/traefik#13368) [@AnatoleLucet](https://github.com/AnatoleLucet)) - **\[server]** Add an option to remove request headers with underscores ([#13262](traefik/traefik#13262) [@youkoulayley](https://github.com/youkoulayley)) - **\[server]** Configurable max request header size ([#13353](traefik/traefik#13353) [@juliens](https://github.com/juliens)) - **\[tls]** Fix nondeterministic TLS certificate selection on shared SAN ([#13348](traefik/traefik#13348) [@rtribotte](https://github.com/rtribotte)) - **\[webui]** Bump axios to v1.18.0 ([#13380](traefik/traefik#13380) [@gndz07](https://github.com/gndz07)) - **\[websocket]** Fix connection upgrades when backend server is using h2c scheme ([#12967](traefik/traefik#12967) [@stffabi](https://github.com/stffabi)) **Documentation:** - **\[k8s/crd]** Fix broken CRD reference links in IngressRoute page ([#13375](traefik/traefik#13375) [@s3onghyun](https://github.com/s3onghyun)) - **\[k8s/gatewayapi]** Remove experimental note for Gateway API/TLSRoute documentation ([#13392](traefik/traefik#13392) [@jnoordsij](https://github.com/jnoordsij)) - **\[k8s/ingress-nginx]** Add Kubernetes Ingress NGINX to the providers list ([#13372](traefik/traefik#13372) [@nmengin](https://github.com/nmengin)) - **\[k8s]** Align Helm chart documented values with chart v41 ([#13366](traefik/traefik#13366) [@mloiseleur](https://github.com/mloiseleur)) - **\[middleware, authentication, k8s/ingress-nginx]** Clarify intentional auth-response-headers gating and absence of stripping incoming X-Forwarded-\* headers ([#13342](traefik/traefik#13342) [@rtribotte](https://github.com/rtribotte)) - **\[middleware]** Clarify entryPoint middleware reference format ([#13364](traefik/traefik#13364) [@mloiseleur](https://github.com/mloiseleur)) - **\[security]** Add HTTP/2 header memory exhaustion security documentation ([#13381](traefik/traefik#13381) [@emilevauge](https://github.com/emilevauge)) - Adds documentations on maxHeaderBytes ([#13363](traefik/traefik#13363) [@juliens](https://github.com/juliens)) - Fix inaccuracies in reference documentation ([#13304](traefik/traefik#13304) [@sheddy-traefik](https://github.com/sheddy-traefik)) ### [`v3.7.6`](https://github.com/containous/traefik/blob/HEAD/CHANGELOG.md#v376-2026-06-30) [Compare Source](traefik/traefik@v3.7.5...v3.7.6) [All Commits](traefik/traefik@v3.7.5...v3.7.6) **Bug fixes:** - **\[acme, logs]** Bump github.com/go-acme/lego/v5 ([#13154](traefik/traefik#13154) [@ldez](https://github.com/ldez)) - **\[acme]** Bump github.com/go-acme/lego/v5 ([#13359](traefik/traefik#13359) [@juliens](https://github.com/juliens)) - **\[k8s, k8s/ingress-nginx]** Fix ingress-nginx ssl passthrough status updates ([#13212](traefik/traefik#13212) [@nickmnt](https://github.com/nickmnt)) - **\[k8s/gatewayapi]** Add missing Gateway API features in conformance tests ([#13356](traefik/traefik#13356) [@AnatoleLucet](https://github.com/AnatoleLucet)) - **\[k8s/gatewayapi]** Avoid collisions for Gateway API services names ([#13367](traefik/traefik#13367) [@rtribotte](https://github.com/rtribotte)) - **\[k8s/gatewayapi]** Ignore other gateways parentRefs and update route parent statuses only for managed gateways ([#13397](traefik/traefik#13397) [@rtribotte](https://github.com/rtribotte)) - **\[k8s/ingress-nginx]** Configure retry according to buffering configuration ([#13039](traefik/traefik#13039) [@rtribotte](https://github.com/rtribotte)) - **\[k8s/ingress-nginx]** Fix force-ssl-redirect routing 418 when TLS is terminated upstream ([#13386](traefik/traefik#13386) [@carloslima](https://github.com/carloslima)) - **\[k8s]** Detect EndpointSlice condition changes ([#13405](traefik/traefik#13405) [@kevinpollet](https://github.com/kevinpollet)) - **\[k8s]** Index Kubernetes EndpointSlice by service name ([#13395](traefik/traefik#13395) [@kevinpollet](https://github.com/kevinpollet)) - **\[k8s]** Sort endpointslices to keep backend IPs consistent across rebuilds ([#13406](traefik/traefik#13406) [@kevinpollet](https://github.com/kevinpollet)) - **\[kv]** Bump kvtools/redis to v1.2.1 ([#13403](traefik/traefik#13403) [@ldez](https://github.com/ldez)) - **\[middleware, authentication]** Fix x-forwarded-port in forward-auth ([#13344](traefik/traefik#13344) [@juliens](https://github.com/juliens)) - **\[middleware, k8s/gatewayapi]** Fix Gateway API redirect missing statuses ([#13360](traefik/traefik#13360) [@AnatoleLucet](https://github.com/AnatoleLucet)) - **\[middleware, k8s/gatewayapi]** Fix Host header not being modified by RequestHeaderModifier ([#12805](traefik/traefik#12805) [@mihuross](https://github.com/mihuross)) - **\[middleware, k8s/gatewayapi]** Fix request scheme derivation when Gateway API RequestRedirect omits scheme ([#13347](traefik/traefik#13347) [@gndz07](https://github.com/gndz07)) - **\[middleware]** Fix CORS Max-Age set to 0 by default ([#13371](traefik/traefik#13371) [@AnatoleLucet](https://github.com/AnatoleLucet)) - **\[middleware]** Fix CORS wildcard when allow-credentials is true ([#13368](traefik/traefik#13368) [@AnatoleLucet](https://github.com/AnatoleLucet)) - **\[server]** Add an option to remove request headers with underscores ([#13262](traefik/traefik#13262) [@youkoulayley](https://github.com/youkoulayley)) - **\[server]** Configurable max request header size ([#13353](traefik/traefik#13353) [@juliens](https://github.com/juliens)) - **\[tls]** Fix nondeterministic TLS certificate selection on shared SAN ([#13348](traefik/traefik#13348) [@rtribotte](https://github.com/rtribotte)) - **\[webui]** Bump axios to v1.18.0 ([#13380](traefik/traefik#13380) [@gndz07](https://github.com/gndz07)) - **\[websocket]** Fix connection upgrades when backend server is using h2c scheme ([#12967](traefik/traefik#12967) [@stffabi](https://github.com/stffabi)) **Documentation:** - **\[k8s/crd]** Fix broken CRD reference links in IngressRoute page ([#13375](traefik/traefik#13375) [@s3onghyun](https://github.com/s3onghyun)) - **\[k8s/gatewayapi]** Remove experimental note for Gateway API/TLSRoute documentation ([#13392](traefik/traefik#13392) [@jnoordsij](https://github.com/jnoordsij)) - **\[k8s/ingress-nginx]** Add Kubernetes Ingress NGINX to the providers list ([#13372](traefik/traefik#13372) [@nmengin](https://github.com/nmengin)) - **\[k8s]** Align Helm chart documented values with chart v41 ([#13366](traefik/traefik#13366) [@mloiseleur](https://github.com/mloiseleur)) - **\[middleware, authentication, k8s/ingress-nginx]** Clarify intentional auth-response-headers gating and absence of stripping incoming X-Forwarded-\* headers ([#13342](traefik/traefik#13342) [@rtribotte](https://github.com/rtribotte)) - **\[middleware]** Clarify entryPoint middleware reference format ([#13364](traefik/traefik#13364) [@mloiseleur](https://github.com/mloiseleur)) - **\[security]** Add HTTP/2 header memory exhaustion security documentation ([#13381](traefik/traefik#13381) [@emilevauge](https://github.com/emilevauge)) - Adds documentations on maxHeaderBytes ([#13363](traefik/traefik#13363) [@juliens](https://github.com/juliens)) - Fix inaccuracies in reference documentation ([#13304](traefik/traefik#13304) [@sheddy-traefik](https://github.com/sheddy-traefik)) </details> --- ### Configuration 📅 **Schedule**: (UTC) - Branch creation - At any time (no schedule defined) - Automerge - At any time (no schedule defined) 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Mend Renovate](https://github.com/renovatebot/renovate).  Reviewed-on: https://git.jfreudenberger.de/JuliusFreudenberger/nix-config/pulls/16 Co-authored-by: Renovate Bot <[email protected]> Co-committed-by: Renovate Bot <[email protected]>

traefiker added area/middleware size/S status/0-needs-triage labels Mar 13, 2026

mmatur added kind/bug/fix a bug fix area/provider/k8s/gatewayapi status/2-needs-review and removed status/0-needs-triage labels Mar 16, 2026

nmengin mentioned this pull request Mar 16, 2026

fix: handle Host header in Gateway API RequestHeaderModifier #12812

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mihuross force-pushed the mh-gatewayapi-header-filter-host branch from bee5aa6 to 1fca88d Compare March 16, 2026 13:43

mihuross changed the base branch from master to v3.6 March 16, 2026 13:44

mmatur added this to the 3.6 milestone Mar 19, 2026

kevinpollet assigned AnatoleLucet Jun 17, 2026

kevinpollet changed the title ~~gateway/headermodifier: Fix Host header not being modified by Request…~~ Fix Host header not being modified by RequestHeaderModifier Jun 18, 2026

kevinpollet force-pushed the mh-gatewayapi-header-filter-host branch from 1fca88d to 25b35d2 Compare June 18, 2026 08:40

kevinpollet approved these changes Jun 18, 2026

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rtribotte approved these changes Jun 18, 2026

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traefiker added bot/merge-retry-1 status/4-merge-in-progress and removed bot/merge-retry-1 labels Jun 18, 2026

mihuross and others added 2 commits June 18, 2026 09:48

gateway/headermodifier: Fix Host header not being modified by Request…

e1fb4ea

…HeaderModifier In Go's net/http, setting the Host header via req.Header.Set is a no-op. The Host header must be set directly on req.Host, similar to what is already done in the customRequestHeaders middleware.

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traefiker force-pushed the mh-gatewayapi-header-filter-host branch from 9e13b90 to 29dd02d Compare June 18, 2026 09:48

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traefiker removed the status/4-merge-in-progress label Jun 18, 2026

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traefiker merged commit 57e5db2 into traefik:v3.6 Jun 18, 2026
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traefiker mentioned this pull request Jun 18, 2026

Gateway API RequestHeaderModifier filter does not modify the Host header #12793

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Fix Host header not being modified by RequestHeaderModifier#12805

Fix Host header not being modified by RequestHeaderModifier#12805
traefiker merged 2 commits into
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mihuross:mh-gatewayapi-header-filter-host

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