CVE-2026-9595: webpack-dev-server Origin Validation Error
CVSS: 5.3v3.1MediumAnalyzed
AliasesUBUNTU-CVE-2026-9595CGA-24p8-mppv-rp5cCGA-27f6-f6mc-qpg3CGA-2xhq-5jv7-qvmpCGA-32f4-gm6g-wx2rCGA-36c9-pvcq-g5r7CGA-3v32-8576-q8m2CGA-4354-4jhj-m3m3CGA-487x-96h2-65hmCGA-4wcf-jggx-x99hCGA-5fqx-6mqp-h6x5CGA-5p8p-xf95-g4q9CGA-835q-m3xc-h7mpCGA-8qg4-275c-67c2CGA-8v67-928x-pwfgCGA-gw7p-7fcj-h7fhCGA-h7cv-g6jm-jwfvCGA-hrmh-wr37-993vCGA-mfw7-9mrq-mgwjCGA-pj9m-mgmh-pwm9CGA-q3rg-mf65-8m6fCGA-r472-r4v6-gmvgCGA-wfmx-pmr3-4wx5CGA-wgr6-wpfr-rw89CGA-wx7x-pr9r-c422CGA-x63f-85r2-qmghCGA-xhwj-vj6x-cfh6GHSA-mx8g-39q3-5c79CGA-25j5-grcq-68v9CGA-2jp9-2rvf-p954CGA-2p98-p282-cjwjCGA-2qxq-f9jc-j43rCGA-3v2w-cw3g-6pj5CGA-4j94-m6jf-2jw6CGA-4m8m-f353-5j2gCGA-55rx-9c8g-74mjCGA-5mr2-v3f5-6h7qCGA-5wqq-g5cf-f5fqCGA-6m3r-cx95-p27xCGA-6vvj-cqg2-8pxmCGA-76f9-6wph-3rp8CGA-8f46-x98p-x4grCGA-8r6m-82j5-4cwxCGA-94cm-p4h2-pmp4CGA-94j8-rw6h-3477CGA-983r-5h72-r3wpCGA-9c8f-737r-m2c7CGA-9rqq-rm8r-fhxcCGA-c8cx-825m-qvvmCGA-cj9j-6665-4rhxCGA-cjjp-7h68-8h24CGA-cp5v-3gvc-4jjqCGA-f8x4-qwf7-5pwjCGA-fc57-c8pp-7g9fCGA-gfhx-v234-fpv9CGA-h4jh-9r75-xgv7CGA-h5fq-2mvm-gqj2CGA-hhxg-m4q4-jhprCGA-hpmj-cwxc-xhx4CGA-hx5h-2r3h-ph97CGA-jc39-qj4q-rwc5CGA-jr5g-7q48-pj39CGA-m85c-q5g5-7775CGA-mjwh-76h6-8cfvCGA-mx9x-cq9r-pg5cCGA-p4j6-889p-3379CGA-p9f6-x632-r5grCGA-pgfx-2v5q-2wqvCGA-q3rf-jphf-qf8hCGA-qf9v-pfx2-4jxxCGA-qw7v-fvrq-79r7CGA-r63m-hqcc-c3q6CGA-rpgp-p4wf-hf6pCGA-rpvj-m537-x5c5CGA-rqw4-m4jv-p3j6CGA-v5wr-jq52-g6pwCGA-v9p8-cr65-pvggCGA-w24p-4rf6-62qrCGA-w55p-5x7c-g4mpCGA-wg7p-ggxc-632rCGA-x67g-43qh-wqhpCGA-xcqj-922q-h6h3CGA-xfc8-8r3c-mqqhCGA-xv8r-4cjc-wj9v
Published 15-06-2026Last modified 15-06-2026
Vulnerability summary
CVE-2026-9595 is a medium (CVSS 5.3) Origin Validation Error vulnerability in webpack-dev-server. EPSS estimates a 0.23% chance of exploitation in the next 30 days, higher than 13.2% of scored vulnerabilities.
CVSS score
5.3/10
010
Medium · v3.1 (CVE.org)EPSS score
0.23%
0%100%
Low · +0.07 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 1 · Related 1Timeline
- 15-06-2026PublishedVulnerability first disclosed.
- 15-06-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
6 scores · 6 sources · 1 versionMedium 5.3Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:LSources6 sources · 4.3–5.3
- OSV · UbuntuEcosystem advisory · calculated4.3MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:LDiffers
- OSV · WolfiEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- OSV · NpmEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- OSV · ChainguardEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- NVDNIST4.3MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:LDiffers
EPSS trend
Probability
0.23%
Chance of exploitation in the next 30 days
Percentile
13%
Versus all other CVEs
30-day change
+0.07 pp
From 0.16% on 20-09-2026
20-09-202620-10-2026
EPSS score0.23%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-346Origin Validation ErrorThe product does not properly verify that the source of data or communication is valid.
- CWE-441Unintended Proxy or Intermediary ('Confused Deputy')The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor.
Affected systems
Chainguard39 products
- arangodb-3.11< 3.11.14.5-r25
- arangodb-3.12< 3.12.11-r0
- argo-workflows-ui-3.6< 3.6.19-r7
- argo-workflows-ui-3.7< 3.7.15-r1
- argo-workflows-ui-4.0< 4.0.6-r1 | < 4.0.11-r0
Wolfi12 products
- argo-workflows-ui-3.7< 3.7.15-r1
- argo-workflows-ui-4.0< 4.0.6-r1 | < 4.0.11-r0
- katib-earlystopping< 0.19.0-r31
- katib-suggestion-goptuna-compatAll versions (No fix recorded)
- katib-suggestion-hyperband< 0.19.0-r31
Ubuntu2 products
- node-webpackAll versions (No fix recorded)
- vue.jsAll versions (No fix recorded)
Npm1 product
- webpack-dev-server< 5.2.5
Webpack-dev-server1 product
- webpack-dev-server< 5.2.5
Webpack.js1 product
- webpack-dev-server< 5.2.5
6 vendors · 56 products
References
10 links- github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79REPORTAdvisoryWEBMitigationVendor Advisory
