Executive brief
Emlog is an open-source website building system that allows administrators to upload plugins and templates as ZIP files. In versions 2.6.29 and earlier, a path traversal vulnerability in the ZIP extraction function allows authenticated attackers to overwrite critical system files like config.php, resulting in immediate remote code execution with web server privileges. This affects plugin uploads, template uploads, and store updates.
Technical details
The vulnerability is a classic Zip Slip path traversal flaw in the emUnZip() function (include/lib/common.php, lines 768–808). The function uses PHP's ZipArchive::extractTo() to extract all ZIP entries without validating individual entry paths for ../ sequences; only the first entry's subdirectory structure is checked. An attacker with admin credentials can craft a malicious ZIP containing entries with paths like "myplugin/../../config.php" to write arbitrary files outside the intended extraction directory. The flaw is exploitable on PHP 7.x and early PHP 8.0.x; later PHP versions may normalize traversal sequences at runtime, but the application performs no path sanitization. The attack vector is authenticated but the impact is critical (RCE via config.php overwrite). No patches are currently available.
Affected products
- Emlog Emlog 2.6.29 and prior
Timeline
- 2026-06-10: disclosed: GHSA-gjj4-37r4-mf5g published
- 2026-09-04: advisory: CVE-2026-53757 published on NVD