CVE-2026-49402: Deno Command Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7xh3-mhg9-jcw8",
  "modified" : "2026-07-20T21:01:31Z",
  "published" : "2026-06-16T19:07:44Z",
  "aliases" : [ "CVE-2026-49402" ],
  "summary" : "Deno: Command Injection via spawnSync & spawn on Windows",
  "details" : "## Summary\n\nDeno's `node:child_process` implementation provided an `escapeShellArg()` helper used when callers passed `shell: true` to `spawn` / `spawnSync` / `exec` and friends. On Windows, the helper failed to quote arguments that contained `cmd.exe` metacharacters such as `&`, `|`, `<`, `>`, `^`, `!`, `(`, `)`, and did not neutralize `%` (which `cmd.exe` expands even inside double-quoted strings). An attacker who controlled any portion of an argument passed to such a call could inject arbitrary additional commands into the spawned `cmd.exe` invocation.\n\nThis was the Windows counterpart to CVE-2026-27190, which fixed the same class of bug in the Unix branch of `escapeShellArg`.\n\n## Details\n\nOn Windows, `child_process` with `shell: true` ran the command via `cmd.exe /d /s /c \"<command line>\"`. Deno assembled that command line by joining the program name and each argument through `escapeShellArg()`.\n\nThe vulnerable check was:\n\n```ts\n// If no special characters, return as-is\nif (!/[\\s\"\\\\]/.test(arg)) {\n  return arg;\n}\n```\n\nThe regex covered only whitespace, double-quote, and backslash. Any argument containing `cmd.exe`-significant characters but none of those three was returned unquoted and therefore interpreted by the shell. The most straightforward exploit chained commands with `&`:\n\n```js\nimport { spawnSync } from \"node:child_process\";\n\nspawnSync(\"echo\", [\"test&calc.exe\"], { shell: true, encoding: \"utf-8\" });\n```\n\nThe reporter confirmed this launched `calc.exe` on Windows 11 with Deno 2.7.5. The same shape worked for `|`, `<`, `>`, `^`, `!`, `(`, and `)`.\n\nA secondary defect existed even when arguments were quoted: `cmd.exe` expands `%FOO%` environment-variable references inside double-quoted strings. Without either doubling `%` or rejecting it, an argument like `\"%USERPROFILE%\"` leaked environment data into the command line.\n\n## Proof of concept\n\nFrom the report, run on Windows with Deno `< 2.7.10`:\n\n```js\nimport { spawnSync } from \"node:child_process\";\n\nconst maliciousInput = \"test&calc.exe\";\nconst result = spawnSync(\"echo\", [maliciousInput], {\n  shell: true,\n  encoding: \"utf-8\",\n});\nconsole.log(result);\n```\n\nObserved: `calc.exe` launched as a side effect of the `echo` call.\n\n## Impact\n\nAny Deno program on Windows that called `child_process.spawn` / `spawnSync` / `exec` (or any shell helper that funneled through `escapeShellArg`) with `shell: true` and incorporated untrusted input into an argument was exposed to arbitrary command execution in the context of the Deno process. The CVSS vector treated this as network-reachable / high-complexity because the typical exposure path was a Deno service accepting external input and forwarding it to a shelled-out subprocess.\n\nNot affected:\n\n- Calls without `shell: true` (the default), which executed the program directly via `CreateProcess` without `cmd.exe` interpretation.\n- Unix platforms, which used the single-quote branch of `escapeShellArg` and were already fixed under CVE-2026-27190.\n- Callers that built command strings themselves and passed them as a single string with `shell: true` — those were the caller's responsibility and were never sanitized by Deno.\n\n## Workarounds\n\nUsers on unpatched versions could mitigate by:\n\n- Avoiding `shell: true` in `node:child_process` calls on Windows.\n- Building the argv directly and invoking the program without a shell.\n- Filtering or rejecting any externally-supplied argument values that contained `cmd.exe` metacharacters (`& | < > ^ ! ( ) %`) before passing them to `spawn` / `spawnSync` / `exec`.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "crates.io",
      "name" : "deno"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.7.10"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/denoland/deno/security/advisories/GHSA-7xh3-mhg9-jcw8"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-49402"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/denoland/deno"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-78" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-16T19:07:44Z",
    "nvd_published_at" : "2026-06-23T18:18:03Z"
  }
}