CVE-2026-6257
Published: 20 April 2026
Summary
CVE-2026-6257 is a critical-severity Unrestricted Upload of File with Dangerous Type (CWE-434) vulnerability. Its CVSS base score is 9.2 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 45.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 CM-7 (Least Functionality) and SI-10 (Information Input Validation).
Deeper analysis
CVE-2026-6257 is a remote code execution vulnerability in Vvveb CMS version 1.0.8, specifically within its media management functionality. The flaw stems from a missing return statement in the file rename handler, which allows authenticated attackers to bypass restrictions and rename uploaded files to blocked extensions such as .php or .htaccess. It carries a CVSS v3.1 base score of 9.1 (AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H) and maps to CWE-434 (Unrestricted Upload of File with Dangerous Type).
Attackers require high privileges (PR:H) to exploit this over the network with low complexity and no user interaction. The scenario involves first uploading a text file and renaming it to .htaccess to inject Apache directives that register PHP-executable MIME types. Attackers can then upload a second file and rename it to .php, achieving arbitrary operating system command execution as the www-data user, with high impact on confidentiality, integrity, and availability due to the changed scope.
A fixing commit is available at https://github.com/givanz/Vvveb/commit/6fb8eaa998265e33e8802cbc220d8859dbc144f2. Further details on the vulnerability and mitigation are provided in the VulnCheck advisory at https://www.vulncheck.com/advisories/vvveb-cms-remote-code-execution-via-media-management.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-23942
Vulnerability details
Vvveb CMS v1.0.8.2 contains a remote code execution vulnerability in its media management functionality where a missing return statement in the file rename handler allows authenticated attackers to rename files to blocked extensions .php or .htaccess. Attackers can exploit this…
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logic flaw by first uploading a text file and renaming it to .htaccess to inject Apache directives that register PHP-executable MIME types, then uploading another file and renaming it to .php to execute arbitrary operating system commands as the www-data user.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The vulnerability in the public-facing Vvveb CMS media management allows authenticated high-privilege attackers to bypass file extension restrictions via rename, enabling web shell deployment (T1505.003) through exploitation of a public-facing application (T1190).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Enforces validation of file names and extensions during rename operations, directly blocking the missing-return bypass that permits .php/.htaccess uploads.
Restricts the media-management component to only safe file-handling capabilities, eliminating the rename-to-executable functionality exploited by the flaw.
Requires malicious-code scanning of all uploaded/renamed files, which would detect the .htaccess MIME-type injection and subsequent PHP payload before execution.