{"id":"GHSA-xc5w-4v5w-7x65","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: ^[^;|&\u003c\u003e]+$ - 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:^[^;|&\u003c\u003e]+$\"\n        title: Custom Input\n```\n3. Trigger RCE via command substitution.\n\n```bash\ncurl -s -X POST http://localhost:1337/api/v1/StartAction \\\n  -H \"Content-Type: application/json\" \\\n  -d '{\"bindingId\":\"custom_input\",\"arguments\":[{\"name\":\"customInput\",\"value\":\"$(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\u003cimg width=\"1533\" height=\"319\" alt=\"olivetin_proof\" src=\"https://github.com/user-attachments/assets/82c9cc50-8f05-41f8-8cee-bceb3d4b3a2d\" /\u003e\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.","aliases":["CVE-2026-67438","GO-2026-6145"],"modified":"2026-08-18T15:10:38.824713547Z","published":"2026-07-30T14:31:12Z","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"},"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"}],"affected":[{"package":{"name":"github.com/OliveTin/OliveTin","ecosystem":"Go","purl":"pkg:golang/github.com/OliveTin/OliveTin"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.0.0-20251025234746-ef5a67e7b8ea"},{"fixed":"0.0.0-20260708084548-995ff79736f2"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-xc5w-4v5w-7x65/GHSA-xc5w-4v5w-7x65.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H"}]}