PT-2026-45020 · Swifturl · Github.Com/Sparkle-Project/Sparkle

Published

2026-05-29

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Updated

2026-05-29

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CVE-2026-47122

CVSS v3.1

4.2

Medium

VectorAV:L/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:L

Summary

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.

Impact

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.

Remediation

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

Fix

Missing Authentication

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Weakness Enumeration

CWE-441CWE-306

Related Identifiers

CVE-2026-47122
GHSA-G3HP-F6MG-559V

Affected Products

Github.Com/Sparkle-Project/Sparkle