Unauthenticated code execution via empty upload allowlist
Published Aug 31, 2026 · Updated Sep 1, 2026
Unrestricted file upload in HashThemes Hash Form 1.4.2 and earlier allows remote attackers to store dangerous files through form submissions. The upload handler turns an attacker-supplied list of unrecognized extensions into an empty allowlist, then treats that empty list as unrestricted. No authentication is required; an excluded file is stored in the uploads folder and served by the site, enabling code execution when the server interprets its type.
Summary
What happened
Unrestricted file upload in HashThemes Hash Form 1.4.2 and earlier allows remote attackers to store dangerous files through form submissions. The upload handler turns an attacker-supplied list of unrecognized extensions into an empty allowlist, then treats that empty list as unrestricted. No authentication is required; an excluded file is stored in the uploads folder and served by the site, enabling code execution when the server interprets its type.
The record
- CVE
- CVE-2026-81780
- Published
- Aug 31, 2026
- Updated
- Sep 1, 2026
- Vendor
- HashThemes
- Product
- Hash Form
- Classifications
- CWE-434, CAPEC-1, T1505.003
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 31, 2026CVE publishedPublication date reported by the CVE source.
- Sep 1, 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?
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- Affected versionversion=n/a <=1.4.2 changes=[{"at":"1.4.3","status":"unaffected"}]
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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