Description
Impact: When a user-configured proxy on webpack-dev-server has a broad context (e.g. /) and ws: true, it also intercepts the dev server's own HMR WebSocket and forwards it to the proxy target. This leaks the browser's cookies and Origin header to the backend, bypasses the dev server's Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket).
Patches: Fixed in webpack-dev-server@5.2.5.
Workarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| webpack-dev-server | webpack-dev-server | < 5.2.5 | 5.2.5 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | vue.js +1 | No fix yet | — |
| Ubuntu 26.04 LTS | vue.js +1 | No fix yet | — |
| Ubuntu 25.10 | vue.js +1 | No fix yet | — |
| Ubuntu 24.04 LTS | vue.js +1 | No fix yet | — |
| Ubuntu 22.04 LTS | vue.js +1 | No fix yet | — |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | vue.js +1 | No fix yet | — |
| Ubuntu 18.04 LTS | node-webpack | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | rh-podman-desktop | 1.1.2-1.el10_2 | RHSA-2026:57590 |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | argo-workflows-ui-4.0 | 4.0.6-r1 | — |
| Wolfi rolling | katib-earlystopping +8 | 0.19.0-r31 | — |
| Wolfi rolling | katib-suggestion-goptuna-compat | 0.19.0-r40 | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| npm | webpack-dev-server | < 5.2.5 | 5.2.5 | GHSA-mx8g-39q3-5c79 |
Advisories 1
- RHSA-2026:57590 Red Hat Security Advisory: rh-podman-desktop security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Oct 20, 2026
References
- https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79
- https://cna.openjsf.org/security-advisories.html
- https://github.com/webpack/webpack-dev-server/pull/4316
- https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcb
- https://github.com/facebook/create-react-app/pull/7444