Atomicorp WAF Research Note: CVE-2026-21875

ClipBucket v5 <= 5.5.2 - Unauthenticated Blind SQL Injection

CVE Details

• Already protected by existing Atomicorp WAF rules
• Protection status: Understanding Atomicorp WAF Protection Status
• CVE: CVE-2026-21875
• Name: ClipBucket v5 <= 5.5.2 - Unauthenticated Blind SQL Injection
• Severity: Critical
• CVSS: 9.8 (v3.1) (Critical)
• CVSS version: 3.1
• CVSS source: GitHub_M CNA
• CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
  • Attack vector: Network
  • Attack complexity: Low
  • Privileges required: None
  • User interaction: None
  • Scope: Unchanged
  • Confidentiality impact: High
  • Integrity impact: High
  • Availability impact: High
• CWE: CWE-89 — Improper Neutralization of Special Elements used in an SQL Command (‘SQL Injection’)
• Related CAPEC attack patterns (via MITRE CWE relationships): CAPEC-108 (opens in a new tab) , CAPEC-109 (opens in a new tab) , CAPEC-110 (opens in a new tab) , CAPEC-470 (opens in a new tab) , CAPEC-66 (opens in a new tab) , CAPEC-7 (opens in a new tab)
• Vendor: macwarrior
• Vulnerable products: clipbucket , clipbucket
• CVE published: 2026-01-08
• CVE last modified: 2026-06-17
• Affected versions (NVD configurations):
  • clipbucket: >= 5.3, < 5.5.2-191
• EPSS: 0.0153; 73.2th percentile (FIRST (opens in a new tab) )
• Latest Update: 2026-09-08
• Selected Rule IDs observed: 341245 , 380122
• Matching rules: 2; rules with blocking actions: 2
• Would-block Rule IDs: 341245 , 380122
• Request surfaces inspected: JSON request data, Request URI, Request argument names, Request arguments, Request cookies, Request headers, SOAP request data, XML request data

Vulnerability Description

ClipBucket v5 is an open source video sharing platform. Versions 5.5.2-#187 and below allow an attacker to perform Blind SQL Injection through the add comment section within a channel. When adding a comment within a channel, there is a POST request to the /actions/ajax.php endpoint. The obj_id parameter within the POST request to /actions/ajax.php is then used within the user_exists function of the upload/includes/classes/user.class. php file as the $id parameter. It is then used within the count function of the upload/includes/classes/db.class. php file. The $id parameter is concatenated into the query without validation or sanitization, and a user-supplied input like 1’ or 1=1– - can be used to trigger the injection. This issue does not have a fix at the time of publication.

Recommended Actions

1. Maintain the observed Atomicorp protections. Keep your Atomicorp commercial rules current and confirm that the selected observed rules (341245 , 380122 ) have not been locally disabled. Atomicorp commercial rules are enabled by default. If you use Atomic WAF, review the applicable policy and rule settings.

2. Apply the vendor’s remediation. WAF protection is defense in depth and does not replace upgrading or following the affected vendor’s guidance.

   • Affected versions: MacWarrior clipbucket-v5 version <= 5.5.2-#187.
   • No specific CNA/vendor solution or workaround is included in the current CVE Record (opens in a new tab) . Review the vendor’s security advisories and supported-release guidance before making changes.

3. Validate after changes. Confirm rule updates are current, review WAF events for the affected application, and test application behavior after vendor upgrades, mitigations, or local policy changes.

Research Notes

Atomicorp WAF protections are designed around attack techniques and exploit behaviors, allowing existing protections to apply across multiple vulnerabilities without requiring a unique rule for every CVE.

Public Vulnerability References

• NVD (opens in a new tab)
• CVE Record (opens in a new tab)
• Vendor advisory: https://github.com/MacWarrior/clipbucket-v5/security/advisories/GHSA-crpv-fmc4-j392 (opens in a new tab)

Test or Research Source

• Source: http/cves/2026/CVE-2026-21875.yaml (opens in a new tab)
• Tags: blind-sqli, clipbucket, cve, cve2026, sqli, time-based, unauth

Research Note Context

This research note documents exploit-technique analysis associated with this vulnerability and references Atomicorp WAF protections observed during engineering review, testing, or validation activities.

Atomicorp security controls are generally designed to identify and mitigate attack techniques and exploit behaviors rather than individual CVE identifiers. As a result, protections developed for one vulnerability may also apply to related attack variants and future vulnerabilities using similar techniques.

Learn More

Atomicorp develops commercially supported security technologies for web applications, servers, endpoints, workloads, and legacy enterprise platforms.

Organizations interested in protecting systems against exploit techniques associated with vulnerabilities such as this one can learn more about:

• Atomic ModSecurity Rules: commercially maintained WAF rules for ModSecurity deployments, including protections for web attacks, bots, scanners, malware, exploitation attempts, and emerging vulnerability classes.
• Atomic WAF: an enterprise web application firewall with Atomicorp rules, centralized management, reporting, authentication controls, and operational tooling.
• Atomic ModSecurity Integrator: a special licensing option for MSPs, MSSPs, OEMs, VARs, reverse proxy providers, and other integrators who want to incorporate Atomicorp ModSecurity rule technology into their own products or services.
• Atomic OSSEC: an enterprise OSSEC-based intrusion detection, compliance, and security monitoring platform.
• Atomic Protector: workload protection for Linux, web, cloud, data center, and hybrid environments.

For additional information, product evaluations, or technical discussions, visit https://www.atomicorp.com/ or https://modsecurity.io/ (opens in a new tab) .