Fix CORS wildcard when allow-credentials is true by AnatoleLucet · Pull Request #13368 · traefik/traefik

AnatoleLucet · 2026-06-16T15:46:17Z

What does this PR do?

This PR fixes two misalignment with the W3C specs on CORS:

[spec] Access-Control-Expose-Headers is now also returned in preflight responses. Before that, it was only returned in non-preflight responses, even though it's supposed to be a preflight-only header.
[spec] when AC-Allow-Credentials is configured to true, the CORS headers in the backend responses shouldn't include wildcards. So when AC-Allow-Credentials is configured as true, the middleware now echos the values from the request in the response's CORS headers instead of returning wildcards.

Motivation

W3C conformance for the upcoming Gateway API CORS filter in the K8s provider.

More

Added/updated tests
Added/updated documentation

Additional Notes

gndz07

LGTM

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 area/provider/k8s area/provider/k8s/gatewayapi size/M status/0-needs-triage labels Jun 16, 2026

traefiker added this to the 3.7 milestone Jun 16, 2026

AnatoleLucet force-pushed the fix/gw-cors-conformance branch from dd55e5e to 58f1ac0 Compare June 18, 2026 09:55

AnatoleLucet changed the base branch from v3.7 to v3.6 June 18, 2026 09:55

AnatoleLucet changed the title ~~Add Gateway API HTTPRoute CORS filter~~ Fix CORS wildcard when allow-credentials is true Jun 18, 2026

kevinpollet added status/2-needs-review kind/bug/fix a bug fix and removed status/0-needs-triage area/provider/k8s area/provider/k8s/gatewayapi labels Jun 18, 2026

kevinpollet modified the milestones: 3.7, 3.6 Jun 18, 2026

AnatoleLucet force-pushed the fix/gw-cors-conformance branch 5 times, most recently from 7fc1880 to 222a6d5 Compare June 22, 2026 14:33

mmatur approved these changes Jun 22, 2026

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kevinpollet assigned gndz07 Jun 22, 2026

gndz07 reviewed Jun 22, 2026

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AnatoleLucet force-pushed the fix/gw-cors-conformance branch from 222a6d5 to 71bb0cb Compare June 23, 2026 07:37

gndz07 approved these changes Jun 23, 2026

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gndz07 added status/3-needs-merge and removed status/2-needs-review labels Jun 23, 2026

traefiker added the status/4-merge-in-progress label Jun 23, 2026

Fix CORS wildcard when allow-credentials is true

8739736

traefiker force-pushed the fix/gw-cors-conformance branch from 71bb0cb to 8739736 Compare June 23, 2026 07:50

traefiker removed the status/4-merge-in-progress label Jun 23, 2026

traefiker merged commit f9d7900 into traefik:v3.6 Jun 23, 2026
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traefiker removed the status/3-needs-merge label Jun 23, 2026

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Fix CORS wildcard when allow-credentials is true#13368

Fix CORS wildcard when allow-credentials is true#13368
traefiker merged 1 commit into
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AnatoleLucet:fix/gw-cors-conformance

AnatoleLucet commented Jun 16, 2026 •

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AnatoleLucet commented Jun 16, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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AnatoleLucet commented Jun 16, 2026 •

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