CVE-2026-9595 (GCVE-0-2026-9595)

Vulnerability from cvelistv5 – Published: 2026-06-15 15:00 – Updated: 2026-06-15 16:08
VLAI
Title
webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies
Summary
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.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-15 16:08 UTC
CWE
  • CWE-346 - Origin Validation Error
  • CWE-441 - Unintended Proxy or Intermediary ('Confused Deputy')
Assigner
References
Impacted products
Vendor Product Version CPE status
webpack-dev-server webpack-dev-server Affected: 0 , < 5.2.5 (semver)
Unaffected: 5.2.5 (semver)
guessed Create a notification for this product.
Credits
bjohansebas UlisesGascon ajhyndman
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-9595",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-15T16:08:24.761216Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-15T16:08:35.549Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "packageURL": "pkg:npm/webpack-dev-server",
          "product": "webpack-dev-server",
          "vendor": "webpack-dev-server",
          "versions": [
            {
              "lessThan": "5.2.5",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "5.2.5",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "coordinator",
          "value": "bjohansebas"
        },
        {
          "lang": "en",
          "type": "analyst",
          "value": "UlisesGascon"
        },
        {
          "lang": "en",
          "type": "remediation developer",
          "value": "ajhyndman"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "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\u0027s own HMR WebSocket and forwards it to the proxy target. This leaks the browser\u0027s cookies and Origin header to the backend, bypasses the dev server\u0027s Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket).\n\nPatches: Fixed in webpack-dev-server@5.2.5.\n\nWorkarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required."
            }
          ],
          "value": "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\u0027s own HMR WebSocket and forwards it to the proxy target. This leaks the browser\u0027s cookies and Origin header to the backend, bypasses the dev server\u0027s Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket).\n\nPatches: Fixed in webpack-dev-server@5.2.5.\n\nWorkarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-346",
              "description": "CWE-346: Origin Validation Error",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-441",
              "description": "CWE-441: Unintended Proxy or Intermediary (\u0027Confused Deputy\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-15T15:00:21.488Z",
        "orgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
        "shortName": "openjs"
      },
      "references": [
        {
          "url": "https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79"
        },
        {
          "url": "https://cna.openjsf.org/security-advisories.html"
        },
        {
          "url": "https://github.com/webpack/webpack-dev-server/pull/4316"
        },
        {
          "url": "https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcb"
        },
        {
          "url": "https://github.com/facebook/create-react-app/pull/7444"
        }
      ],
      "title": "webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies",
      "x_generator": {
        "engine": "cve-kit 1.0.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
    "assignerShortName": "openjs",
    "cveId": "CVE-2026-9595",
    "datePublished": "2026-06-15T15:00:21.488Z",
    "dateReserved": "2026-05-26T14:38:47.772Z",
    "dateUpdated": "2026-06-15T16:08:35.549Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-9595",
      "date": "2026-08-20",
      "epss": "0.00163",
      "percentile": "0.05991"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-9595\",\"sourceIdentifier\":\"ce714d77-add3-4f53-aff5-83d477b104bb\",\"published\":\"2026-06-15T16:16:35.227\",\"lastModified\":\"2026-06-17T11:05:31.643\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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\u0027s own HMR WebSocket and forwards it to the proxy target. This leaks the browser\u0027s cookies and Origin header to the backend, bypasses the dev server\u0027s Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket).\\n\\nPatches: Fixed in webpack-dev-server@5.2.5.\\n\\nWorkarounds: 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\":[{\"source\":\"ce714d77-add3-4f53-aff5-83d477b104bb\",\"affectedData\":[{\"vendor\":\"webpack-dev-server\",\"product\":\"webpack-dev-server\",\"defaultStatus\":\"unaffected\",\"packageURL\":\"pkg:npm/webpack-dev-server\",\"versions\":[{\"version\":\"0\",\"lessThan\":\"5.2.5\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"5.2.5\",\"versionType\":\"semver\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"ce714d77-add3-4f53-aff5-83d477b104bb\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L\",\"baseScore\":5.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"LOW\"},\"exploitabilityScore\":3.9,\"impactScore\":1.4},{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L\",\"baseScore\":4.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"LOW\"},\"exploitabilityScore\":2.8,\"impactScore\":1.4}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-06-15T16:08:24.761216Z\",\"id\":\"CVE-2026-9595\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"yes\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"ce714d77-add3-4f53-aff5-83d477b104bb\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-346\"},{\"lang\":\"en\",\"value\":\"CWE-441\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:webpack.js:webpack-dev-server:*:*:*:*:*:*:*:*\",\"versionEndExcluding\":\"5.2.5\",\"matchCriteriaId\":\"C902F68B-A783-4F64-A2D5-6C09220D0CCA\"}]}]}],\"references\":[{\"url\":\"https://cna.openjsf.org/security-advisories.html\",\"source\":\"ce714d77-add3-4f53-aff5-83d477b104bb\",\"tags\":[\"Vendor Advisory\"]},{\"url\":\"https://github.com/facebook/create-react-app/pull/7444\",\"source\":\"ce714d77-add3-4f53-aff5-83d477b104bb\",\"tags\":[\"Issue Tracking\",\"Patch\"]},{\"url\":\"https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcb\",\"source\":\"ce714d77-add3-4f53-aff5-83d477b104bb\",\"tags\":[\"Patch\"]},{\"url\":\"https://github.com/webpack/webpack-dev-server/pull/4316\",\"source\":\"ce714d77-add3-4f53-aff5-83d477b104bb\",\"tags\":[\"Issue Tracking\",\"Patch\"]},{\"url\":\"https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79\",\"source\":\"ce714d77-add3-4f53-aff5-83d477b104bb\",\"tags\":[\"Mitigation\",\"Vendor Advisory\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-08-20T20:32:05+00:00",
      "cve": "CVE-2026-9595",
      "id": "CVE-2026-9595",
      "initial_release_date": "2026-06-15T15:00:21.488000+00:00",
      "product_status:fixed": "29",
      "product_status:known_affected": "23",
      "product_status:known_not_affected": "2886",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "webpack-dev-server: webpack-dev-server: Information disclosure and denial of service via improper proxy configuration",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-9595.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-07-03T03:26:58Z",
      "cve": "CVE-2026-9595",
      "id": "CVE-2026-9595",
      "initial_release_date": "2026-07-03T03:26:58Z",
      "product_status:known_affected": "8",
      "product_status:known_not_affected": "379",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-9595",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-9595.json",
      "version": "2"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-9595\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-06-15T16:08:24.761216Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-06-15T16:08:30.548Z\"}}], \"cna\": {\"title\": \"webpack-dev-server vulnerable to HMR WebSocket interception via permissive user proxies\", \"credits\": [{\"lang\": \"en\", \"type\": \"coordinator\", \"value\": \"bjohansebas\"}, {\"lang\": \"en\", \"type\": \"analyst\", \"value\": \"UlisesGascon\"}, {\"lang\": \"en\", \"type\": \"remediation developer\", \"value\": \"ajhyndman\"}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV3_1\": {\"version\": \"3.1\", \"baseScore\": 5.3, \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"webpack-dev-server\", \"product\": \"webpack-dev-server\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"5.2.5\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.2.5\", \"versionType\": \"semver\"}], \"packageURL\": \"pkg:npm/webpack-dev-server\", \"defaultStatus\": \"unaffected\"}], \"references\": [{\"url\": \"https://github.com/webpack/webpack-dev-server/security/advisories/GHSA-mx8g-39q3-5c79\"}, {\"url\": \"https://cna.openjsf.org/security-advisories.html\"}, {\"url\": \"https://github.com/webpack/webpack-dev-server/pull/4316\"}, {\"url\": \"https://github.com/vuejs/vue-cli/commit/72ba7505aff2a8314e82aa5082379a77504a1fcb\"}, {\"url\": \"https://github.com/facebook/create-react-app/pull/7444\"}], \"x_generator\": {\"engine\": \"cve-kit 1.0.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"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\u0027s own HMR WebSocket and forwards it to the proxy target. This leaks the browser\u0027s cookies and Origin header to the backend, bypasses the dev server\u0027s Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket).\\n\\nPatches: Fixed in webpack-dev-server@5.2.5.\\n\\nWorkarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"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\u0027s own HMR WebSocket and forwards it to the proxy target. This leaks the browser\u0027s cookies and Origin header to the backend, bypasses the dev server\u0027s Host/Origin validation, and corrupts the HMR socket (both HMR and the proxy end up writing to the same socket).\\n\\nPatches: Fixed in webpack-dev-server@5.2.5.\\n\\nWorkarounds: Scope user-defined proxy context to specific paths instead of /, or omit ws: true from the proxy entry when WebSocket forwarding is not required.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-346\", \"description\": \"CWE-346: Origin Validation Error\"}]}, {\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-441\", \"description\": \"CWE-441: Unintended Proxy or Intermediary (\u0027Confused Deputy\u0027)\"}]}], \"providerMetadata\": {\"orgId\": \"ce714d77-add3-4f53-aff5-83d477b104bb\", \"shortName\": \"openjs\", \"dateUpdated\": \"2026-06-15T15:00:21.488Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-9595\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-06-15T16:08:35.549Z\", \"dateReserved\": \"2026-05-26T14:38:47.772Z\", \"assignerOrgId\": \"ce714d77-add3-4f53-aff5-83d477b104bb\", \"datePublished\": \"2026-06-15T15:00:21.488Z\", \"assignerShortName\": \"openjs\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.