{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "actix-http"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.12.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-444"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-22T14:37:30Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "A vulnerability in `actix-http`\u0027s HTTP/1.1 request parser allows an unauthenticated remote client to smuggle requests in deployments where a front-end HTTP intermediary and the Actix backend disagree about whether `Content-Length` or `Transfer-Encoding: chunked` defines the request body length.\n\n## Severity\n\n**Medium**.\nThis is an HTTP request smuggling vulnerability that can be triggered over the network without application-level credentials. Exploitation requires a specific proxy topology: an upstream proxy, WAF, load balancer, or similar intermediary must use `Content-Length` framing while forwarding the conflicting `Transfer-Encoding: chunked` request to an Actix backend over a reused HTTP/1.1 connection.\n\n## Affected Versions\n\n- `actix-http`: versions up to and including **3.12.0**\n\n## Description\n\nHTTP/1.1 requests that contain both `Content-Length` and `Transfer-Encoding: chunked` are ambiguous and must be rejected by recipients to avoid request smuggling.\n\nAffected versions of `actix-http` accepted a request with a syntactically valid `Content-Length` header and `Transfer-Encoding: chunked` on the same HTTP/1.1 message. The parser then selected chunked decoding instead of rejecting the conflicting framing signals.\n\nIn a CL.TE proxy topology, an intermediary may treat bytes after the declared `Content-Length` body as part of the first request, while the Actix backend stops at the terminating chunk marker and parses the remaining bytes on the backend connection as a second HTTP request. This creates a backend-side request desynchronization primitive.\n\nThe issue is limited to HTTP/1.1 request parsing.\n\n## Impact\n\n**HTTP request smuggling**\n\n* **Attack Vector:** Network, unauthenticated.\n* **Effect:** Backend request desynchronization with low integrity impact to requests processed by the vulnerable Actix service.\n* **Scope:** Actix services using affected `actix-http` versions behind an HTTP/1.1 intermediary that forwards ambiguous `Content-Length` plus `Transfer-Encoding: chunked` requests and reuses backend connections.\n\nNo direct confidentiality, availability, or subsequent-system impact is scored for this advisory.\n\n## Fixed Versions\n\nThis issue is fixed in **actix-http 3.12.1**.\n\nThe fix rejects HTTP/1.1 requests that contain both `Content-Length` and `Transfer-Encoding: chunked` instead of choosing one framing interpretation.\n\n## Mitigation\n\nUsers should upgrade to **actix-http 3.12.1** or later.\n\nApplications that depend on `actix-http` through `actix-web`, `awc`, or another Actix crate should ensure dependency resolution selects `actix-http` 3.12.1 or later. For example:\n\n```bash\ncargo update -p actix-http\n```\n\nIf an immediate upgrade is not possible, configure all upstream HTTP intermediaries to reject HTTP/1.1 requests that contain both `Content-Length` and `Transfer-Encoding`, and avoid forwarding ambiguous request framing to Actix backends.\n## Credits\n\nActix thanks [mufeedvh](https://github.com/mufeedvh) who disclosed this issue through coordinated disclosure.",
  "id": "GHSA-xhj4-vrgc-hr34",
  "modified": "2026-04-22T14:37:30Z",
  "published": "2026-04-22T14:37:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/actix/actix-web/security/advisories/GHSA-xhj4-vrgc-hr34"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/actix/actix-web"
    },
    {
      "type": "WEB",
      "url": "https://github.com/actix/actix-web/releases/tag/http-v3.12.1"
    },
    {
      "type": "WEB",
      "url": "https://www.rfc-editor.org/rfc/rfc9112.html#name-message-body-length"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "actix-http has HTTP/1.1 CL.TE Request Smuggling "
}