CVE-2026-55231

Executive Summary

CVE-2026-55231 is a path traversal vulnerability in the Vvveb CMS affecting versions prior to 1.0.8.6. An authenticated attacker with backup access (default site_admin role or higher) can exploit a flawed central path sanitizer to read and delete arbitrary files on the underlying server. The impact is severe — confidentiality, integrity, and availability are all rated High — enabling database credential theft, host file disclosure (e.g., /etc/passwd), and site takeover by deleting config/db.php to force re-installation. No public PoC, Nuclei template, or exploit code is currently available, and no patch evidence has been confirmed by tracked sources.

Technical Analysis

The vulnerability is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory / Path Traversal). The root cause, per the NVD description, is a flawed central path sanitizer — a single, centrally-located routine responsible for validating user-supplied path input across the backup functionality. Because this sanitizer is defective, path segments containing traversal sequences (../) or absolute path prefixes are not adequately normalized or rejected before being passed to file read/delete operations.

The attack surface is the backup feature of the Vvveb admin panel. The NVD description explicitly states that the flaw is reachable by "an authenticated admin-panel user who holds backup access (default role site_admin or higher)." This confirms:

• Authentication is required — aligns with CVSS PR:H (Privileges Required: High), meaning the attacker must already possess valid credentials with elevated permissions.
• The sanitizer is central — a single shared routine is used by the backup read and delete code paths, so a single bypass affects both operations.
• Impact spans read and delete — traversal enables both arbitrary file read (confidentiality) and arbitrary file deletion (integrity/availability).

The following concrete file paths are explicitly named in the NVD description and are relevant to the attack:

• config/db.php — contains database credentials; readable for credential theft, deletable to force install mode.
• /etc/passwd — cited as an example of an arbitrary host file that can be read.

No further implementation detail (specific function names, HTTP parameter names, or module endpoints) is available in the provided data. Any additional specifics would be speculative and are therefore omitted. What is certain from the description is the vulnerability class (path traversal), the choke point (central path sanitizer), the preconditions (authenticated backup privilege), and the dual read/delete capability.

Because the CVSS vector is AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H, the flaw is network-reachable with low attack complexity, requires no user interaction, and does not cross a security scope boundary — but requires high (administrative) privileges to trigger.

Exploitation Scenarios

The following chain is inferred strictly from the NVD description and the vulnerability class; no public PoC exists.

1. Reconnaissance / target identification. An attacker identifies a Vvveb CMS instance (e.g., via the admin login page or fingerprinted assets) running a version prior to 1.0.8.6.

2. Prerequisite access. The attacker obtains credentials for an admin-panel account holding backup access. Per the description, the default qualifying role is site_admin or higher. This could come from credential reuse, phishing, a leaked credential dump, or a separate initial-access vulnerability. The vulnerability itself does not grant this access.

3. Triggering the traversal (class-level). Using the backup functionality, the attacker submits a crafted path value into the backup read/delete request. The value contains directory traversal sequences (or an absolute path prefix) intended to escape the intended backup directory. Because the central path sanitizer fails to properly normalize or constrain the path, the supplied value is accepted and used to resolve the target file.

4. Payload / execution (class-level). The attacker specifies target paths such as config/db.php (for credential read or deletion) or /etc/passwd (for host file read). Since the read function returns file contents and the delete function removes the resolved file, the same sanitizer bypass supports both actions. No code execution is required — this is a file-system-level read/delete primitive.

5. Post-exploitation impact.

   • Credential theft: Reading config/db.php yields database credentials, enabling direct database access, data exfiltration, or lateral movement.
   • Host disclosure: Reading files such as /etc/passwd exposes local account information for further enumeration.
   • Full takeover: Deleting config/db.php pushes the site back into install mode. If the application then permits re-installation without adequate safeguards, the attacker can complete a fresh install and take over the site.

No public PoC available; attack chain is inferred from the vulnerability class.

Impact Assessment

Business impact is high across all three security objectives:

• Confidentiality (C:H): Arbitrary file read exposes secrets such as database credentials in config/db.php and host files such as /etc/passwd. This can cascade into database compromise and credential reuse attacks against other systems.
• Integrity (I:H): Arbitrary file deletion lets the attacker remove critical configuration files. Deleting config/db.php specifically reverts the application to an unconfigured/install state.
• Availability (A:H): Removal of configuration or other essential files can render the site inoperable until restored, and the re-install state enables potential full site takeover.

Affected systems: All Vvveb CMS deployments (websites, blogs, ecommerce stores) running versions prior to 1.0.8.6 where an admin-level backup-capable account can be obtained.

Blast radius: The direct blast radius is the compromised host (file read/delete) and any database whose credentials are recovered from config/db.php. Because a full site takeover is achievable via the install-mode path, the secondary blast radius includes all site data, customer records, and any ecommerce transactions. Note the prerequisites: the attacker must already hold authenticated site_admin (or higher) backup access, which constrains the initial-access bar but not the resulting impact. Deployment on shared hosting expands the relevance of host-file disclosure (e.g., /etc/passwd).

Detection Guidance

Sigma Rule

title: Vvveb CMS Backup Path Traversal File Access (CVE-2026-55231)
id: 3f7c9a2e-1b4d-4e8a-9c21-52d3b6a7e0f1
status: experimental
description: Detects path traversal sequences in requests to Vvveb backup functionality, targeting sensitive files like config/db.php or /etc/passwd.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-55231
author: Valters IT Threat Intelligence
date: 2026/01/01
logsource:
  category: webserver
  product: generic
detection:
  selection_traversal:
    cs-uri-query|contains:
      - '../'
      - '..%2f'
      - '%2e%2e%2f'
      - '%2e%2e/'
      - '....//'
  selection_targets:
    cs-uri-query|contains:
      - 'db.php'
      - 'passwd'
      - 'config/'
      - '%2fetc%2f'
      - '/etc/'
  selection_backup:
    cs-uri|contains:
      - 'backup'
  condition: selection_backup and (selection_traversal or selection_targets)
falsepositives:
  - Legitimate administrative file management with normalized paths
level: high

YARA Rule

rule CVE_2026_55231_Vvveb_Path_Traversal_Attempt
{
    meta:
        description = "Detects potential path traversal exploitation attempts against Vvveb CMS backup functionality in HTTP/web logs"
        author = "Valters IT Threat Intelligence"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-55231"
        date = "2026-01-01"

    strings:
        $t1 = "../" ascii nocase
        $t2 = "..%2f" ascii nocase
        $t3 = "%2e%2e%2f" ascii nocase
        $t4 = "....//" ascii nocase
        $s1 = "db.php" ascii nocase
        $s2 = "/etc/passwd" ascii nocase
        $s3 = "%2fetc%2fpasswd" ascii nocase
        $b1 = "backup" ascii nocase

    condition:
        $b1 and (any of ($t*)) and (any of ($s*))
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-55231 Vvveb CMS Backup Path Traversal Attempt"; flow:established,to_server; http.uri; content:"backup"; nocase; http.uri; pcre:"/(%2e%2e|\\.\\.)(%2f|\\/)/i"; http.uri; content:"db.php"; nocase; sid:202655231; rev:1; metadata:attack_target Web_Server, cve CVE-2026-55231, deployment Perimeter, signature_severity High; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-55231; classtype:web-application-attack;)

Elastic Detection

sequence by source.ip with maxspan=5s
  [any where event.category == "web" and
      stringContains(url.query, "..") and
      (stringContains(url.query, "db.php") or
       stringContains(url.query, "passwd") or
       stringContains(url.query, "config/")) and
      stringContains(url.path, "backup") and
      http.response.status_code == 200]

Splunk SPL Query

index=web sourcetype=access_combined OR sourcetype=nginx:access
| eval uri_lower = lower(uri), query_lower = lower(uri_query)
| where (like(uri_lower, "%backup%"))
| where (like(query_lower, "%..%") OR like(query_lower, "%2e%2e%2f%") OR like(query_lower, "%....%"))
  AND (like(query_lower, "%db.php%") OR like(query_lower, "%passwd%") OR like(query_lower, "%config/%") OR like(query_lower, "%/etc/%"))
| stats count min(_time) as first_seen max(_time) as last_seen values(uri) as uris by src_ip, user_agent
| where count > 0
| sort - count

Wazuh OSSEC Rule

<group name="web,appsec,vvveb,">
  <rule id="100231" level="12">
    <decoded_as>json</decoded_as>
    <field name="url">backup</field>
    <match>\.\./|%2e%2e%2f|\.\.%2f|\.\.\.\.//</match>
    <description>CVE-2026-55231: Possible Vvveb CMS backup path traversal attempt (directory traversal sequence detected).</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_55231,path_traversal,</group>
  </rule>

  <rule id="100232" level="13">
    <if_sid>100231</if_sid>
    <field name="url">db\.php|passwd|/etc/|config/</field>
    <description>CVE-2026-55231: Vvveb backup traversal targeting sensitive file (config/db.php or host file).</description>
    <mitre>
      <id>T1190</id>
      <id>T1005</id>
    </mitre>
    <group>cve_2026_55231,sensitive_file_access,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source). The NVD description states the issue is patched in version 1.0.8.6; however, no vendor advisory URL, commit hash, or release artifact confirming that patch has been located by tracked sources. Treat remediation as unverified until the vendor fix can be independently confirmed.

1. Immediate mitigations (until patch is verified):

   • Restrict the backup-capable roles. Review all accounts holding site_admin or higher and remove backup access from any account that does not strictly require it.
   • Implement network-side filtering (WAF/reverse proxy) to reject requests to backup functionality containing traversal sequences (../, ..%2f, %2e%2e%2f) or references to sensitive paths (config/db.php, /etc/, passwd).
   • Enforce strong, unique credentials and MFA on all admin-panel accounts to reduce the likelihood of an attacker satisfying the PR:H precondition.
   • Move config/db.php credentials to environment variables or a secrets manager where feasible, reducing the value of both the read and delete primitives.
   • Ensure the application cannot be re-installed on a live instance (re-install lock) to blunt the config/db.php deletion takeover path.

2. Patch / upgrade steps:

   • Upgrade Vvveb CMS to version 1.0.8.6 or later as referenced in the NVD description.
   • Because no patch evidence was confirmed, independently verify the fix by reviewing the vendor changelog/repository for the change to the central path sanitizer before relying on the upgrade alone.
   • After upgrading, re-test the backup read/delete paths with controlled traversal inputs in a staging environment.

3. Long-term hardening:

   • Replace ad-hoc path validation with canonicalization (realpath) plus strict allow-listing against a fixed backup directory root; reject any resolved path outside the permitted base.
   • Apply the principle of least privilege to backup functionality and separate read from delete permissions.
   • Deploy file integrity monitoring on config/db.php and other critical configuration files to detect unexpected modification or deletion.
   • Maintain regular, offline backups and tested restore procedures to recover rapidly from destructive file deletion.

References

• NVD — CVE-2026-55231: https://nvd.nist.gov/vuln/detail/CVE-2026-55231
• CWE-22 — Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'): https://cwe.mitre.org/data/definitions/22.html
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
• CISA Known Exploited Vulnerabilities Catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog (CVE-2026-55231 is NOT listed as of this report)
• Vvveb CMS project repository (consult vendor changelog for the 1.0.8.6 fix): https://github.com/givanz/Vvveb

No public proof-of-concept, Nuclei template, or exploit code is currently available. No threat actor campaigns or exploit-in-the-wild evidence have been identified for CVE-2026-55231, and the vulnerability is not included in CISA KEV. EPSS has not yet been scored by FIRST.org.