CVE-2026-47122

AppInstaller post-stage-1 XPC listener accepts unvalidated connections, allowing spoofed appcast item data injection.

Details

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.

The following chain of events enables an attacker to inject a spoofed SPUSentUpdateAppcastItemData payload:

1. Installer finishes unarchiving the update successfully (_willCompleteInstallation is set).
2. 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.
3. 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.
4. 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).

Note: 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.

In 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.

Affected versions: 2.x branch including 2.9.1.

A 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.

The 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.

A critical operation is accessible without requiring any authentication. Typical impact: any user can invoke the privileged function.

CVE-2026-47122 has a CVSS score of 4.2 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

Enforce SUCodeSigningVerifier validateConnection: on all new connections regardless of installation stage, or disallow SPUSentUpdateAppcastItemData after the active connection invalidates.

1. What is CVE-2026-47122? CVE-2026-47122 is a medium-severity missing authentication for critical function vulnerability in github.com/sparkle-project/Sparkle (swift), affecting versions <= 2.9.1. No fixed version is listed yet. A critical operation is accessible without requiring any authentication.
2. How severe is CVE-2026-47122? CVE-2026-47122 has a CVSS score of 4.2 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/sparkle-project/Sparkle are affected by CVE-2026-47122? github.com/sparkle-project/Sparkle (swift) versions <= 2.9.1 is affected.
4. Is there a fix for CVE-2026-47122? No fixed version is listed for CVE-2026-47122 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2026-47122 exploitable, and should I be worried? Whether CVE-2026-47122 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-47122 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-47122? No fixed version is listed yet. In the interim: Keep the dependency up to date. Add authentication gating to all sensitive endpoints.