Authenticated code execution via SHTML upload
Published Aug 18, 2026 · Updated Aug 19, 2026
Unrestricted file upload in Joomla! CMS before 5.4.8 and 6.1.3 allows remote authenticated users to execute code via SHTML uploads. The upload checks in Joomla CMS and its Filesystem package rely on forbidden-extension lists, and the published flaw is that the default dangerous-file list omitted shtml, letting a server-executable file type pass validation. Exploitation requires high-privilege access to a reachable upload path and a server configuration that executes SHTML files; when both conditions hold, the uploaded content can run with the web server's privileges.
Summary
What happened
Unrestricted file upload in Joomla! CMS before 5.4.8 and 6.1.3 allows remote authenticated users to execute code via SHTML uploads. The upload checks in Joomla CMS and its Filesystem package rely on forbidden-extension lists, and the published flaw is that the default dangerous-file list omitted shtml, letting a server-executable file type pass validation. Exploitation requires high-privilege access to a reachable upload path and a server configuration that executes SHTML files; when both conditions hold, the uploaded content can run with the web server's privileges.
The record
- CVE
- CVE-2026-73373
- Published
- Aug 18, 2026
- Updated
- Aug 19, 2026
- Vendor
- Joomla! Project
- Product
- Joomla! Framework Filesystem Package
- Classifications
- CWE-434, T1505.003
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Aug 18, 2026CVE publishedPublication date reported by the CVE source.
- Aug 19, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=1.0.0-3.3.0
- Affected versionversion=4.0.0-4.2.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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