CVE-2026-67438: Github.com/OliveTin/OliveTin Argument Type Bypassing Shell Safety Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xc5w-4v5w-7x65",
  "modified" : "2026-07-30T14:31:12Z",
  "published" : "2026-07-30T14:31:12Z",
  "aliases" : [ "CVE-2026-67438" ],
  "summary" : "OliveTin OS Command Injection via Custom regex: Argument Type Bypassing Shell Safety Check",
  "details" : "### Summary\nOliveTin's checkShellArgumentSafety() function maintains a blocklist of argument types unsafe for Shell mode actions, but does not include regex:-prefixed types. Because regex: support was added independently via typeSafetyCheckRegex(), any Shell mode action using a regex:-typed argument bypasses the safety check unconditionally. The unvalidated value is then interpolated directly into the sh -c command string via Go's text/template with no escaping, enabling shell injection. Notably, even restrictive-looking patterns are exploitable — for example, a pattern blocking common shell metacharacters remains bypassable via POSIX command substitution.\n\n### Details\nOliveTin is an open source web UI for running pre-configured shell commands. In the OliveTin service component, the function checkShellArgumentSafety() in service/internal/executor/arguments.go enforces a blocklist of argument types that are unsafe for use in Shell mode actions (actions that execute via sh -c). The blocklist includes password, very_dangerous_raw_string, url, email, and raw_string_multiline. It does not handle custom regex: prefixed argument types.\n\nCustom regex: types are supported by a separate function, typeSafetyCheckRegex(), which checks whether a submitted value matches the provided pattern. These two functions evolved independently: when regex: prefix support was added to typeSafetyCheckRegex, checkShellArgumentSafety was not updated to treat regex: types as unsafe for Shell mode. As a result, any action configured with a Shell mode handler and a regex:-typed argument passes the safety check unconditionally, regardless of how permissive or restrictive the pattern is.\n\nThe argument value then reaches handleShellBranch → wrapCommandInShell, where Go's text/template interpolates it directly into the sh -c command string with no escaping.\n\nCritically, this vulnerability is not limited to obviously permissive patterns like regex:.*. An admin who writes a restrictive-looking pattern such as regex: ^[^;|&<>]+$ - explicitly blocking the five most common shell injection characters (semicolon, pipe, ampersand, both redirects) — is still fully exploitable via POSIX command substitution.\n\n\n### PoC\n1. Deploy OliveTin\n```bash\ndocker run -d --name olivetin-poc -p 1337:1337 \\\n  -v /tmp/olivetin-poc/config:/config \\\n  ghcr.io/olivetin/olivetin:3000.11.3\n```\n2. Write the configuration below as /tmp/olivetin-poc/config/config.yaml , which represents a realistic admin-authored action: a Shell mode command that accepts user-supplied input validated by a custom regex pattern.\n```yaml\nactions:\n  - title: Custom Input Action\n    id: custom_input\n    shell: echo \"Input was {{ .Arguments.customInput }}\"\n    arguments:\n      - name: customInput\n        type: \"regex:^[^;|&<>]+$\"\n        title: Custom Input\n```\n3. Trigger RCE via command substitution.\n\n```bash\ncurl -s -X POST http://localhost:1337/api/v1/StartAction \\\n  -H \"Content-Type: application/json\" \\\n  -d '{\"bindingId\":\"custom_input\",\"arguments\":[{\"name\":\"customInput\",\"value\":\"$(touch /tmp/rce_proof)\"}]}'\n```\n4. Now verify RCE by checking presence of file\n```bash\ndocker exec olivetin-poc ls -la /tmp/rce_proof\n```\n<img width=\"1533\" height=\"319\" alt=\"olivetin_proof\" src=\"https://github.com/user-attachments/assets/82c9cc50-8f05-41f8-8cee-bceb3d4b3a2d\" />\n\n\n### Impact\nAn unauthenticated attacker with network access to an OliveTin instance can achieve full OS command injection - and in practice remote code execution — as the OliveTin process user, provided a Shell mode action exists with any regex:-typed argument whose pattern permits $, backtick, or parentheses.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/OliveTin/OliveTin"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0.0.0-20251025234746-ef5a67e7b8ea"
      }, {
        "fixed" : "0.0.0-20260708084548-995ff79736f2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/OliveTin/OliveTin/security/advisories/GHSA-xc5w-4v5w-7x65"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-67438"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/OliveTin/OliveTin/commit/995ff79736f2bccc364448a3ece84087b550b232"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/OliveTin/OliveTin"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/OliveTin/OliveTin/releases/tag/3000.17.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-78" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-30T14:31:12Z",
    "nvd_published_at" : "2026-07-29T21:17:48Z"
  }
}