CVE-2026-81891: elFinder ZIP extraction MIME filter bypass allowing PHP upload

CVE-2026-81891 · Severity: high · CVSS 8.1 · Published 2026-08-31

elFinder is a popular file manager library used in web applications. The vulnerability allows users who can upload ZIP files to extract PHP executable files that bypass the administrator's upload restrictions, leading to remote code execution. An attacker could place a malicious PHP script in a ZIP archive, upload it, extract it, and then execute it to completely compromise the web server and underlying application.

Technologies: studio-42/elfinder (Packagist), Studio-42 elFinder. Vendors: Packagist, Studio-42.

Quick answers

Is CVE-2026-81891 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-81891 being exploited in the wild.
How severe is CVE-2026-81891?
High severity, with a CVSS score of 8.1, published 31 August 2026.
Which products and versions are affected?
studio-42/elfinder (Packagist) < 2.1.70, ECOSYSTEM:introduced=0,fixed=2.1.70; Studio-42 elFinder < 2.1.70.
Is there a fix for CVE-2026-81891?
Yes. studio-42/elfinder (Packagist): upgrade to 2.1.70 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-81891 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-81891?
Check whether you run studio-42/elfinder (Packagist) or Studio-42 elFinder 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.

How to fix

  • studio-42/elfinder (Packagist): upgrade to 2.1.70 or later
    composer require studio-42/elfinder:^2.1.70

Technical details

The vulnerability is a filter bypass in the ZIP extraction command (CWE-434: Unrestricted Upload of File with Dangerous Type). The root cause is inconsistent MIME validation logic: the direct file upload path calls mimetypeInternalDetect() → mimeTypeNormalize() → allowPutMime(), but the extract command (checkExtractItems() at line 7110 of elFinderVolumeDriver.class.php) calls only mimetypeInternalDetect() → allowPutMime(), skipping the normalization stage. Because .phtml, .phar, .php5, and .php3 are absent from the system mime.types database, they return generic types (e.g., application/octet-stream) instead of text/x-php. Without mimeTypeNormalize(), the staticMimeMap that maps these extensions to text/x-php is never applied. An authenticated attacker can create a ZIP containing a PHP payload file with one of these extensions, upload it (bypassing ZIP validation), and extract it, placing executable PHP in a web-accessible directory. On default Apache/Nginx setups, the extracted file is then executable. The fix (confirmed in 2.1.70) applies mimeTypeNormalize() within checkExtractItems() to enforce consistent validation.

Affected products

  • Studio-42 elFinder < 2.1.70

Identifiers

  • CVE-2026-81891
  • GHSA-gxmj-r5rf-ggwq

Timeline

  • 2026-08-03: disclosed: vulnerability reported to GitHub Advisory Database
  • 2026-09-02: advisory: GHSA-gxmj-r5rf-ggwq published; CVE-2026-81891 assigned
  • 2026-09-02: patched: patch released in elFinder 2.1.70
  • 2026-08-31: other: NVD published CVE-2026-81891 details

References

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