{"id":"GHSA-pp9r-xg4c-8j4x","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","aliases":["CVE-2026-33241"],"modified":"2026-03-25T21:04:54.069030Z","published":"2026-03-19T12:44:56Z","database_specific":{"nvd_published_at":"2026-03-24T00:16:29Z","cwe_ids":["CWE-770"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-03-19T12:44:56Z"},"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"}],"affected":[{"package":{"name":"salvo","ecosystem":"crates.io","purl":"pkg:cargo/salvo"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"0.89.3"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-pp9r-xg4c-8j4x/GHSA-pp9r-xg4c-8j4x.json"}}],"schema_version":"1.9.0","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"}]}