CVE-2026-33241: Salvo Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-pp9r-xg4c-8j4x",
  "modified" : "2026-03-25T20:48:57Z",
  "published" : "2026-03-19T12:44:56Z",
  "aliases" : [ "CVE-2026-33241" ],
  "summary" : "Salvo Affected by Denial of Service via Unbounded Memory Allocation in Form Data Parsing",
  "details" : "## Summary\nSalvo's form data parsing implementations (`form_data()` method and `Extractible` macro) do not enforce payload size limits before reading request bodies into memory. This allows attackers to cause Out-of-Memory (OOM) conditions by sending extremely large payloads, leading to service crashes and denial of service.\n\n## Details\n### Vulnerability Description\nThree attack vectors exist in Salvo's form handling:\n\n1. **URL-encoded form data** (`application/x-www-form-urlencoded`)\n   - `Request::form_data()` calls `BodyExt::collect(body)` which reads the entire body into memory without size checking\n   - Affects handlers using `req.form_data().await` directly\n\n2. **Multipart form data** (`multipart/form-data`)\n   - Similar unbounded memory allocation during parsing\n   - Affects handlers processing multipart uploads\n\n3. **Extractible macro**\n   - `#[derive(Extractible)]` with `#[salvo(extract(default_source(from = \"body\")))]` internally calls `form_data()`\n   - Vulnerabilities propagate to all extractors using body sources\n\n### Root Cause\nThe `FormData::read()` implementation prioritizes convenience over safety by reading entire request bodies before validation. Even when `Request::payload_with_max_size()` is available, it's not automatically applied in the form parsing path.\n\n### PoC\n1. run `Extract data from request` example in readme.md in docker file with limited memory say 100mb.\n2. Send `application/x-www-form-urlencoded` OR `multipart/form-data` payload to the endpoint.\n3. The server process OOM-crashes, instead of returning 413 error.\n\n\n## Impact\n### Immediate Effects\n- **Service Unavailability**: Servers crash under memory pressure\n- **Resource Exhaustion**: Single request can consume all available memory\n- **Cascading Failures**: In containerized environments, OOM can affect other services\n\n### Attack Characteristics\n- **Low Cost**: Attacker needs minimal bandwidth (header only, body can be streamed)\n- **No Authentication**: Exploitable on public endpoints\n- **Difficult to Rate-Limit**: Traditional rate limiting may not prevent single large request\n- **Amplification**: Small network cost → large memory consumption\n\n### Real-World Scenarios\n1. Public API endpoints accepting form data\n2. User registration/profile update handlers\n3. File upload endpoints using multipart forms\n4. Any endpoint using `#[derive(Extractible)]` with body sources\n\n## Suggestion: Make Multipart File Upload Handling Explicit Opt-In\n\n### Problem Statement\n\nCurrently, Salvo's multipart form data parsing automatically handles file uploads without explicit developer intent. This creates several security and usability concerns:\n\n1. **Unintended File Storage**: Developers may unknowingly accept file uploads when they only intended to handle text fields\n2. **Disk Space Exhaustion**: Automatic file buffering to disk can fill storage without proper limits\n3. **Resource Cleanup**: Temporary files may not be properly cleaned up if handlers don't expect them\n4. **Attack Surface**: Endpoints inadvertently become file upload targets",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "salvo"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.89.3"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/salvo-rs/salvo/security/advisories/GHSA-pp9r-xg4c-8j4x"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33241"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/salvo-rs/salvo"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/salvo-rs/salvo/releases/tag/v0.89.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-19T12:44:56Z",
    "nvd_published_at" : "2026-03-24T00:16:29Z"
  }
}