Cloudanix VulnDB

CVE-2026-47121

Medium · 6.1

Sparkle: Binary delta apply intermediate-symlink traversal in malicious .delta

CVSS

6.1

EPSS

0.3%

Published

May 29, 2026

CISA due date

—

The record

Binary delta apply intermediate-symlink traversal in malicious .delta `Autoupdate/SUBinaryDeltaApply.m` enforces `relativePath.pathComponents containsObject:@".."` and rejects writes whose immediate parent directory IS itself a symbolic link, but does not detect symlinks deeper in the relative path. `Autoupdate/SPUSparkleDeltaArchive.m`'s `extractItem:` will create symlinks in the destination tree from archive content (no `..` check on the symlink target), and a subsequent `Extract` item targeting `<symlink>/foo/bar` then escapes the destination tree via `fopen(path, "wb")` because the kernel resolves the intermediate symlink during the open call. This is a defense-in-depth issue: exploitation requires a maliciously-crafted `.delta` that passes EdDSA signature verification, i.e. EdDSA private-key compromise. With the AppInstaller running as root for system-domain installs, it gives the holder of a stolen signing key arbitrary file write at root level via the delta-apply path, which is a strictly broader primitive than the "drop-in replacement bundle" install they would otherwise have. Affected versions: 1.x (master branch), 2.x branch including 2.9.1.

Affected packages

Ecosystem Package Introduced Fixed

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