CVE-2026-48861: Mint Mint Has Potential CRLF Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2pg6-44cx-c49v",
  "modified" : "2026-07-09T23:19:12Z",
  "published" : "2026-07-09T23:19:12Z",
  "aliases" : [ "CVE-2026-48861" ],
  "summary" : "mint has potential CRLF injection in its HTTP request line via unvalidated `method`/`target`",
  "details" : "### Summary\n\nMint's HTTP/1 request encoder splices the caller-supplied `method` and `target` directly into the request line without character validation. An application that forwards attacker-controlled input as the HTTP method or the target to `Mint.HTTP.request/5` is exposed to request-line CRLF injection, allowing the attacker to terminate the request line early, inject arbitrary headers, and pipeline a fully attacker-chosen second request onto the same TCP connection.\n\n### Details\n\n`encode_request_line/2` in `lib/mint/http1/request.ex` writes `method` and `target` to the wire verbatim. `encode_headers/1` validates header names and values, but there is no equivalent `validate_method!/1`.\n\nMint 1.7.0 added `validate_request_target/2`, which rejects CRLF and other control characters in `target` by default and closes the path/query vector. The `method` field remains unvalidated, so a CRLF-bearing method such as `\"GET / HTTP/1.1\\r\\nX-Smuggled: 1\\r\\nGET /admin\"` is accepted and written to the socket as-is. Bytes after the first `\\r\\n` are interpreted by the peer as an injected header, or, with a second `\\r\\n`, as an additional pipelined request.\n\n### PoC\n\n1. Stand up a Mint-using gateway/proxy that calls `Mint.HTTP.request(conn, method, \"/\", [], nil)` with `method` taken from caller input.\n2. Send a request whose forwarded method is `\"GET / HTTP/1.1\\r\\nX-Smuggled-Header: pwned\\r\\nGET /admin/delete-everything\"`.\n3. Observe the bytes received by the upstream server: the smuggled header line and the second request line appear verbatim in the outbound stream.\n\n### Impact\n\nCRLF injection / HTTP request smuggling in the HTTP/1 client encoder, exploitable under default configuration whenever an application passes caller-influenced input as the HTTP method. An attacker who controls the method can inject arbitrary outbound headers (forged `Host`, `Authorization`, cache-poisoning headers) and smuggle additional, fully attacker-chosen requests to the upstream server over the same connection, potentially reaching endpoints the legitimate caller never intended to invoke.\n\n## Resources\n\n* Introduction commit: https://github.com/elixir-mint/mint/commit/8db1acff30b6a9433762c18b1e1f891b8c1f74f7\n* Patch commit: https://github.com/elixir-mint/mint/commit/fad091454cbb7449b19edb8e1fee12ca7cf28c3a",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Hex",
      "name" : "mint"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.9.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/elixir-mint/mint/security/advisories/GHSA-2pg6-44cx-c49v"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-48861"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/elixir-mint/mint/commit/fad091454cbb7449b19edb8e1fee12ca7cf28c3a"
  }, {
    "type" : "WEB",
    "url" : "https://cna.erlef.org/cves/CVE-2026-48861.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/elixir-mint/mint"
  }, {
    "type" : "WEB",
    "url" : "https://osv.dev/vulnerability/EEF-CVE-2026-48861"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-93" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-09T23:19:12Z",
    "nvd_published_at" : "2026-06-02T16:16:44Z"
  }
}