Quick answers
- Is CVE-2026-78839 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-78839 being exploited in the wild.
- How severe is CVE-2026-78839?
- High severity, with a CVSS score of 8.1, published 4 September 2026.
- Which products and versions are affected?
- AppNitro MachForm v30.
- Is there a fix for CVE-2026-78839?
- No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
- How is CVE-2026-78839 attacked?
- It is attacked over the network, in a web application.
- Am I affected by CVE-2026-78839?
- Check whether you run AppNitro MachForm at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
The vulnerability is an arbitrary file upload flaw in MachForm v30's upload.php endpoint that allows .phar files to be uploaded when explicitly configured as permitted file types. The uploaded files are assigned MD5-based filenames and stored on the web-accessible server. An attacker can retrieve and execute the uploaded .phar file either by brute-forcing the random MD5 hash filename (unlimited requests are permitted) or by leveraging secondary vulnerabilities that disclose the filename. Exploitation requires either a form pre-configured to accept .phar uploads, or sufficient access rights to modify form upload settings. The attack results in remote code execution with server privileges.
Affected products
- AppNitro MachForm v30
Timeline
- 2026-09-04: disclosed