CVE-2026-47122: Github.com/sparkle project/Sparkle Sparkle's AppInstaller Post-stage-1 XPC Listener Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-g3hp-f6mg-559v",
  "modified" : "2026-05-29T19:47:19Z",
  "published" : "2026-05-29T19:47:19Z",
  "aliases" : [ "CVE-2026-47122" ],
  "summary" : "Sparkle's AppInstaller post-stage-1 XPC listener accepts unvalidated connections, allowing spoofed appcast item data injection",
  "details" : "## Summary\n\nAppInstaller post-stage-1 XPC listener accepts unvalidated connections, allowing spoofed appcast item data injection.\n\n## Details\n\n`Autoupdate/AppInstaller.m`'s `shouldAcceptNewConnection:` only enforces `SUCodeSigningVerifier validateConnection:` before stage 1 completes. After `_performedStage1Installation = YES`, new connections to the registered Mach service `<bundleId>-spki` are accepted from any local process without team-ID or code-signing checks.\n\nThe following chain of events enables an attacker to inject a spoofed `SPUSentUpdateAppcastItemData` payload:\n\n1. Installer finishes unarchiving the update successfully (`_willCompleteInstallation` is set).\n2. The app responsible for updating the bundle crashes or is forcefully quit before it has a chance to send `SPUSentUpdateAppcastItemData` to the installer. There is no user interaction between the prior step and this one, so the timing window is tight.\n3. After stage 1 of the installer is performed (`_performedStage1Installation = YES`), but before final installation completes (since all services are cleaned up by then), an attacker process connects to the `<bundleId>-spki` Mach service - no code-signing validation is enforced - and sends a spoofed `SPUSentUpdateAppcastItemData` message containing an attacker-crafted `SUAppcastItem`.\n4. A Sparkle-aware app that checks for updates on the bundle being updated launches before installation completes. The progress agent re-broadcasts the spoofed `SUAppcastItem` on its `<bundleId>-spks` status service, and the launching app displays attacker-controlled release notes (name, version, critical flag).\n\nNote: Sparkle can be used to update other app bundles, so the \"app doing the updating\" and the \"app being updated\" are not necessarily the same bundle.\n\nIn the system-domain case (`SPUUsesSystemDomainForBundlePath = true`), the AppInstaller runs as root via `SMJobSubmit` to `kSMDomainSystemLaunchd`, and the Mach service is reachable by any local user process.\n\nAffected versions: 2.x branch including 2.9.1.\n\n## Impact\n\nA local user-level process can inject a forged `SUAppcastItem` (arbitrary name, version, critical flag) into the progress agent's status broadcast. Other Sparkle-aware clients on the system will display attacker-controlled release notes as authoritative installation state.\n\nThe integrity of the installed code is **not** affected - the bundle moved into place is the legitimate, signature-validated update from stage 1. The impact is limited to UI spoofing of installation metadata.\n\n## Remediation\n\nEnforce `SUCodeSigningVerifier validateConnection:` on all new connections regardless of installation stage, or disallow `SPUSentUpdateAppcastItemData` after the active connection invalidates.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "SwiftURL",
      "name" : "github.com/sparkle-project/Sparkle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "2.9.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sparkle-project/Sparkle/security/advisories/GHSA-g3hp-f6mg-559v"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sparkle-project/Sparkle"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-306", "CWE-441" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-29T19:47:19Z",
    "nvd_published_at" : null
  }
}