CVE-2026-86540: Knowns Knowns OS Command Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mc52-mwq4-vfx3",
  "modified" : "2026-10-06T18:58:38Z",
  "published" : "2026-10-06T18:58:38Z",
  "aliases" : [ "CVE-2026-86540" ],
  "summary" : "knowns OS Command Injection via Insecure LSP Binary Path Config in .knowns/config.json",
  "details" : "## Overview\n\nA critical **Arbitrary Code Execution (ACE)** vulnerability exists in the Knowns Language Server Protocol (LSP) detection and startup pipeline. The system blindly trusts the `settings.lsp.languages.<lang>.binary` field defined in the project-level `.knowns/config.json` file. \n\nBecause this field is **never validated** against an allowlist of managed binaries, and absolute paths are implicitly accepted, opening a malicious repository (or a legitimate repository where the config has been tampered with) results in the immediate execution of an attacker-controlled binary. The payload is executed **twice** per session: once during the initial `runVersionCheck` (health check), and again when the LSP server process is spawned via `Server.Start()`. When chained with the previously identified Config Overwrite vulnerabilities, this flaw yields a fully unauthenticated Remote Code Execution chain.\n\n## Affected paths\n\n| File Path | Role | Vulnerability & Execution Impact |\n| :--- | :--- | :--- |\n| **`internal/models/config.go`** | Validation Gap | **Missing Binary Validation (CWE-829):** `ProjectSettings.Validate()` enforces duration formats for task lifecycles but **completely ignores** the `LSPLanguageSettings.Binary` field. Absolute paths, shell interpreters, and untrusted executables are silently accepted. |\n| **`internal/lsp/detect.go`** | Execution Sink #1 | **Unsanitized Health Check Execution:** `Detector.resolve()` passes the unvalidated override to `exec.LookPath()`, then invokes `runVersionCheck()` which blindly calls `cmd.Run()` on the attacker-controlled binary with `CheckArgs`. |\n| **`internal/lsp/server.go`** | Execution Sink #2 | **Unsanitized LSP Server Spawn:** `Server.Start()` passes the resolved binary path to `knownsprocess.Command()` and spawns it as a long-running background process via `cmd.Start()`, executing the payload a second time. |\n\n## Root Cause\n\n### Missing Validation in Configuration Schema\nIn `internal/models/config.go`, the `ProjectSettings.Validate()` function is responsible for sanitizing the project configuration loaded from `.knowns/config.json`. However, it only validates task lifecycle durations:\n\n```go\nfunc (s ProjectSettings) Validate() error {\n    settings := s.EffectiveTaskLifecycle()\n    if _, err := ParseTaskLifecycleDuration(settings.ArchiveAfter); err != nil { ... }\n    // NO VALIDATION FOR s.LSP.Languages[lang].Binary\n    return nil\n}\n```\n\nThe `LSPLanguageSettings` struct exposes a `Binary` string field. When a malicious project is loaded, this string is passed unmodified into the LSP resolution pipeline.\n\n### Blind Execution in LSP Detector\nIn `internal/lsp/detect.go`, the `Detector.resolve()` function accepts an `override` string (from the config) and forces it into the execution pipeline:\n\n```go\nfunc (d *Detector) resolve(ctx context.Context, root string, lang Language, override string) (ServerCommand, bool) {\n    binaries := lang.Binaries\n    if override != \"\" {\n        binary := Binary{Name: override} // Attacker's malicious path injected here\n        binaries = []Binary{binary}\n    }\n    for _, binary := range binaries {\n        path, err := d.LookPath(binary.Name) // Accepts absolute paths (e.g., /tmp/evil.sh)\n        // ...\n        err = d.RunCheck(checkCtx, path, binary.CheckArgs...) // EXECUTION #1\n        // ...\n    }\n}\n```\n\n`d.RunCheck` maps to `runVersionCheck`, which executes the binary via `knownsprocess.CommandContext(ctx, path, args...).Run()`.\n\n### Unrestricted Process Spawn\nIn `internal/lsp/server.go`, when the LSP manager starts the server, it executes the same compromised path:\n\n```go\nfunc (s *Server) Start(ctx context.Context) error {\n    // ...\n    cmd := knownsprocess.Command(s.Command.Path, s.Command.Args...) // EXECUTION #2\n    cmd.Dir = s.Root\n    // ...\n    if err := cmd.Start(); err != nil { ... }\n}\n```\n\n## Attack Vector\n\n| Phase | Request / Action | Effect |\n| :--- | :--- | :--- |\n| **1. Plant** | Attacker commits `.knowns/config.json` containing `{\"settings\":{\"lsp\":{\"languages\":{\"go\":{\"binary\":\"/tmp/evil.sh\"}}}}}` to a repository. | Malicious config embedded in the project. |\n| **2. Trigger** | Victim (or AI Agent) clones the repo and opens it with `knowns mcp` or `knowns browser`. | Auto-detection scans the project, finds a `.go` file, and loads the malicious config. |\n| **3. Execute (Health Check)** | `Detector.resolve()` calls `runVersionCheck(\"/tmp/evil.sh\", \"version\")`. | **RCE Execution #1** occurs silently in the background. |\n| **4. Execute (LSP Spawn)** | `Server.Start()` calls `cmd.Start()` with the same binary. | **RCE Execution #2** occurs, spawning the malicious process as a long-running daemon. |\n\n**Chained Attack Vector (Unauthenticated RCE):**\nIf combined with the **Config Overwrite** vulnerability (via `code.replace` path traversal), a remote attacker can overwrite `.knowns/config.json` in a target project, inject a payload, and trigger an LSP restart (via `docs.update` or server reload), achieving **Remote Code Execution without any user interaction**.\n\n## Analysis\n\nThis vulnerability is a textbook example of **Inclusion of Functionality from Untrusted Control Sphere (CWE-829)**, commonly known in the IDE/Editor space as the \"Malicious Workspace\" vulnerability (similar to historical CVEs in VS Code where `.vscode/settings.json` could point to malicious interpreter paths).\n\nThe core failure is the lack of a strict allowlist for executable paths. By relying on `exec.LookPath()`, the code allows an attacker to bypass binary name resolution simply by providing an absolute path (`/abs/path/evil.sh`) or a path containing a slash (`./evil.sh`). \n\nFurthermore, the execution happens **automatically** upon project load. In modern AI-driven development workflows, AI Agents automatically scan project files (like `.go`, `.ts`, `.py`) to provide context. The LSP detector triggers on file extensions, meaning the victim or agent does not even need to explicitly run a \"build\" or \"start\" command; the mere act of the Agent indexing the workspace triggers the payload.\n\n## Fix\n\n*Patch is available right now at [New Release](https://github.com/knowns-dev/knowns/releases).*",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "knowns"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.30.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.29.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/knowns-dev/knowns/security/advisories/GHSA-mc52-mwq4-vfx3"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-86540"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/knowns-dev/knowns/commit/d3989829fb5095666d23d005b2f78a082832a396"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/knowns-dev/knowns"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/lsp/detect.go#L128-L157"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/knowns-dev/knowns/blob/v0.29.1/internal/models/config.go#L205-L216"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/knowns-dev/knowns/releases/tag/v0.30.0"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/knowns-before-0.30.0-arbitrary-code-execution-via-lsp-binary"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-427", "CWE-78", "CWE-829", "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-06T18:58:38Z",
    "nvd_published_at" : null
  }
}