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GHSA-CRQ5-92J2-J7WV

Vulnerability from github – Published: 2026-09-15 20:01 – Updated: 2026-09-15 20:01
VLAI
Summary
Http4s: ResourceService and Webjar Service path escape via percent-encoded separators
Details

The static content handlers ResourceService and WebjarService URL decode each path segment and then reject only segments that are exactly "", ".", or "..". A percent-encoded separator (%2F) lets an attacker smuggle a ../ segment past that filter and escape the configured base, reading resources that should not be public.

On Windows, a similar attack exists with (%5C).

Impact

Disclosure of classpath or webjar resources outside the configured base.

Preconditions

  • Application uses ResourceService (with a non-root base path) or WebjarService
  • At least one classpath entry is served from a directory (e.g. sbt run, exploded .war)
  • Backend forwards %2F/%5C without normalizing (e.g., Ember, Blaze)

Fixes

The patch rejects any decoded path segment containing / (%2F) or \ (%5C) with a 400 Bad Request in ResourceService and WebjarService.

FileService was not exploitable, but the same guards are applied for consistency and to remove its reliance on path normalization.

Workarounds

  • Deploy as a fat jar, with no filesystem directories on the classpath.
  • Front the service with a proxy that rejects/normalizes %2F and %5C in the request path.
Severity
5.9 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Show details on source website
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.34"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-server_2.12"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.34"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-server_2.13"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.34"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-server_3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.0.0-M46"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-server_3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0-M1"
            },
            {
              "fixed": "1.0.0-M47"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.0.0-M46"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-server_2.13"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0-M1"
            },
            {
              "fixed": "1.0.0-M47"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-69201"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-15T20:01:12Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "The static content handlers `ResourceService` and `WebjarService` URL decode each path segment and then reject only segments that are exactly `\"\"`, `\".\"`, or `\"..\"`.  A percent-encoded separator (`%2F`) lets an attacker smuggle a `../` segment past that filter and escape the configured base, reading resources that should not be public.\n\nOn Windows, a similar attack exists with (`%5C`).\n\n## Impact\n\nDisclosure of classpath or webjar resources outside the configured base.\n\n## Preconditions\n\n- Application uses `ResourceService` (with a non-root base path) or `WebjarService`\n- At least one classpath entry is served from a directory (e.g. `sbt run`, exploded .war)\n- Backend forwards `%2F`/`%5C` without normalizing (e.g., Ember, Blaze)\n\n## Fixes\n\nThe patch rejects any decoded path segment containing `/` (`%2F`) or `\\` (`%5C`) with a `400 Bad Request` in `ResourceService` and `WebjarService`.\n\n`FileService` was not exploitable, but the same guards are applied for consistency and to remove its reliance on path normalization.\n\n## Workarounds\n\n- Deploy as a fat jar, with no filesystem directories on the classpath.\n- Front the service with a proxy that rejects/normalizes `%2F` and `%5C` in the request path.",
  "id": "GHSA-crq5-92j2-j7wv",
  "modified": "2026-09-15T20:01:13Z",
  "published": "2026-09-15T20:01:12Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/http4s/http4s/security/advisories/GHSA-crq5-92j2-j7wv"
    },
    {
      "type": "WEB",
      "url": "https://github.com/http4s/http4s/commit/bcd99cdc1342ef58a0f132acb814af06a668a8d3"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/http4s/http4s"
    },
    {
      "type": "WEB",
      "url": "https://github.com/http4s/http4s/releases/tag/v0.23.35"
    },
    {
      "type": "WEB",
      "url": "https://github.com/http4s/http4s/releases/tag/v1.0.0-M47"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Http4s: ResourceService and Webjar Service path escape via percent-encoded separators"
}



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