{"id":"CVE-2026-47122","aliases":["GHSA-g3hp-f6mg-559v"],"url":"https://o3.security/vulnerability/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.","published":"2026-07-21T13:57:59.824Z","modified":"2026-08-12T03:51:22.729785427Z","cvss":{"score":4.2,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:L"},"epss":{"score":0.00078,"percentile":0.00141,"asOf":"2026-08-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"SwiftURL","name":"github.com/sparkle-project/Sparkle","fixedVersion":null}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/47xxx/CVE-2026-47122.json"},{"type":"ADVISORY","url":"https://github.com/sparkle-project/Sparkle/security/advisories/GHSA-g3hp-f6mg-559v"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47122"},{"type":"PACKAGE","url":"https://github.com/sparkle-project/Sparkle"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:22.729785427Z"}}