CVERadar
CRITICAL · CVSS 4.0 9.4EPSS 0.64% (p51)Threat level 47

CVE-2026-126378: CVE-2026-126378: Vvveb through 1.0.8.6 contains a file upload vulnerability in the theme installer validFil…

Unknown · Vvveb · NVD published 2026-11-13 · posted 2026-11-13 · last modified 2026-11-13

CVE-2026-126378 at a glance

CVE-2026-126378 is a critical-severity File Upload vulnerability in Vvveb, with a CVSS 4.0 base score of 9.4. NVD published it on 2026-11-13 and classifies the weakness as CWE-434. FIRST EPSS puts the probability of exploitation activity in the next 30 days at 0.64% (percentile 51.0, scored 2026-11-14). NVD does not list a fixed version, so the vendor advisory is the reference for the fix. CVERadar maps 3 MITRE ATT&CK techniques across Initial Access, Persistence and Execution, inferred from the CWE and the description. Its CVERadar threat level is 47/100.

What it is

Vvveb through 1.0.8.6 contains a file upload vulnerability in the theme installer validFile() function that uses strpos() instead of strict path matching. Attackers with admin credentials can upload a ZIP containing a PHP file whose path includes /theme.php to achieve remote code execution on nginx deployments.

WeaknessCWE-434 definition
CVSS vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X (source: VulnCheck)
ATT&CK tacticsInitial Access → Execution → Persistence

Defend the Chain

The attack chain for CVE-2026-126378 laid across the MITRE ATT&CK Enterprise tactics. Solid cards come from the MITRE CTID KEV mappings; dashed cards are inferred by CVERadar from the CWE or description. Correct defences are real ATT&CK mitigations for that technique.

Threat level 47/100
Defender level 1 · 0 XP
Chain links broken: 0/3

Reconnaissance

Resource Development

Initial Access

Execution

Persistence

Privilege Escalation

Stealth

Defense Impairment

Credential Access

Discovery

Lateral Movement

Collection

Command and Control

Exfiltration

Impact

Pick a red technique card on the board, then choose the defence that stops it.

Defend against T1190 Exploit Public-Facing Application Inferred

Inferred from CWE CWE-434

Patches, mitigations and detection

Fixed versions

NVD does not list a fixed version for this CVE. Use the vendor advisory below.

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

No vendor-tagged reference yet; see the full reference list.

MITRE ATT&CK mitigations for this chain

  • M1048 Application Isolation and Sandboxing (for T1190, T1203) : Application isolation will limit what other processes and system features the exploited target can access.
  • M1037 Filter Network Traffic (for T1190) : Restrict outbound network traffic from public-facing servers to prevent unauthorized connections from initiating communications with attacker-controlled infrastructure. While this may not prevent the initial exploitation, it limits the attacker's ability to verify and control the compromised server post-exploit, reduci
  • M1030 Network Segmentation (for T1190) : Segment externally facing servers and services from the rest of the network with a DMZ or on separate hosting infrastructure.
  • M1016 Vulnerability Scanning (for T1190) : Regularly scan externally facing systems for vulnerabilities and establish procedures to rapidly patch systems when critical vulnerabilities are discovered through scanning and through public disclosure.
  • M1026 Privileged Account Management (for T1190) : Use least privilege for service accounts will limit what permissions the exploited process gets on the rest of the system.
  • M1050 Exploit Protection (for T1190, T1203) : Web Application Firewalls may be used to limit exposure of applications to prevent exploit traffic from reaching the application.
  • M1035 Limit Access to Resource Over Network (for T1190) : Ensure that all publicly exposed services are actually intended to be so, and restrict access to any that should only be available internally.
  • M1051 Update Software (for T1190, T1203) : Update software regularly by employing patch management for externally exposed applications.
  • M1042 Disable or Remove Feature or Program (for T1505.003) : Consider disabling functions from web technologies such as PHP’s `evaI()` that may be abused for web shells.
  • M1018 User Account Management (for T1505.003) : Enforce the principle of least privilege by limiting privileges of user accounts so only authorized accounts can modify the web directory.

Detection Generic guidance

  • Initial Access: Alert on unusual requests to the affected service (odd paths, oversized payloads, exploit strings) in WAF, reverse-proxy and application logs.
  • Execution: Watch for the service process spawning shells or script interpreters (cmd.exe, powershell, sh, bash, python) via EDR process-tree rules.
  • Persistence: Look for new files in web roots, new scheduled tasks/services, and new accounts created after the exposure window.

Response checklist Generic guidance

  1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
  2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
  3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
  4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.

Sources