CVE-2026-77928: ClipBucket SQL Injection Vulnerability

CVE-2026-77928 Overview

CVE-2026-77928 is a blind SQL injection vulnerability [CWE-89] in ClipBucket v5 versions prior to 5.5.3-#182. The flaw resides in the private message deletion handler, where the msg_id parameter can be submitted as an array to bypass the clean_requests() sanitization function in ClipBucket.class.php. Authenticated attackers can extract arbitrary database contents, including user credential hashes and email addresses, through time-based blind SQL injection.

Critical Impact

Any authenticated ClipBucket user can exfiltrate full database contents, including password hashes and email addresses, by sending a crafted array parameter to the message deletion endpoint.

Affected Products

• ClipBucket v5 versions before 5.5.3-#182
• The private_message.php deletion handler
• The cb_pm::delete_msg() method interpolating msg_id into SQL

Discovery Timeline

• 2026-09-18 - CVE-2026-77928 published to NVD
• 2026-09-22 - Last updated in NVD database

Technical Details for CVE-2026-77928

Vulnerability Analysis

The vulnerability exists in ClipBucket v5's private messaging subsystem. When a user requests deletion of a private message, the private_message.php handler forwards the msg_id parameter to the cb_pm::delete_msg() method. That method concatenates the parameter directly into a SQL query without escaping or parameterization.

ClipBucket relies on the clean_requests() function in ClipBucket.class.php to sanitize request parameters globally. However, clean_requests() operates on scalar string values and does not recursively sanitize array elements. Attackers exploit this gap by submitting msg_id as an array, which passes through sanitization unmodified and reaches the vulnerable query.

Because the deletion endpoint does not return query results directly, attackers use time-based inference. A payload that conditionally invokes SLEEP() or BENCHMARK() reveals data one bit at a time through response latency, enabling extraction of the entire users table.

Root Cause

The root cause is inadequate input sanitization combined with unsafe SQL string interpolation. The clean_requests() routine assumes scalar inputs, so array-typed request parameters bypass filtering. cb_pm::delete_msg() compounds the flaw by building queries with string concatenation instead of prepared statements, satisfying the conditions for [CWE-89] SQL Injection.

Attack Vector

The attack requires network access and a valid authenticated session on the target ClipBucket instance. An attacker submits a POST request to the private message deletion endpoint with msg_id[] structured as an array containing SQL payload fragments. The server processes the array element inside the DELETE query, causing time-based side effects that leak database contents.

// Security patch reference - upload/changelog/553.json
 {
   "version":"5.5.3",
-  "revision":"178",
+  "revision":"179",
   "status":"stable",
   "detail":[
     {
// Source: https://github.com/MacWarrior/clipbucket-v5/commit/85907c5fd1205ccae98c214bed4b3421c632f90c
// Changelog entry: "Miscellaneous : Fix possible SQL injection (Thanks @QwesiRED !), Cleanup code"

Detection Methods for CVE-2026-77928

Indicators of Compromise

• HTTP POST requests to private_message.php containing array-style parameters such as msg_id[]= in the request body
• Request payloads that include SQL keywords such as SLEEP, BENCHMARK, SELECT, UNION, or IF( within msg_id values
• Anomalous latency in responses from the message deletion endpoint, particularly repeated requests with incrementally changing payloads

Detection Strategies

• Inspect web server access logs for msg_id[] array notation directed at ClipBucket handlers
• Deploy web application firewall rules that flag array-typed parameters where the application expects scalar integer IDs
• Correlate authenticated user sessions with high-volume repetitive POST traffic to private_message.php, a signature of blind SQLi enumeration

Monitoring Recommendations

• Enable MySQL general query logging on the ClipBucket database and alert on DELETE statements containing SLEEP( or BENCHMARK(
• Track outbound HTTP response times from the deletion endpoint and alert on latency spikes consistent with time-based injection
• Monitor for unusual read patterns against the users table, especially queries that select password or email columns from authenticated sessions

How to Mitigate CVE-2026-77928

Immediate Actions Required

• Upgrade ClipBucket v5 to release 5.5.3-#182 or later, which contains the upstream fix in commit 85907c5
• Audit application logs for prior exploitation attempts targeting private_message.php and rotate all user credentials if evidence of extraction is found
• Restrict access to authenticated ClipBucket features via IP allowlists or reverse proxy authentication until patching is complete

Patch Information

The vendor released the fix in the ClipBucket 5.5.3-#182 release. The corresponding upstream commit 85907c5 addresses the SQL injection and includes broader code cleanup. Full technical analysis is available in the VulnCheck SQL Injection Advisory.

Workarounds

• If immediate patching is not possible, add a web application firewall rule to reject any request to ClipBucket endpoints where msg_id is submitted as an array
• Temporarily disable the private messaging feature by removing or restricting access to private_message.php at the web server level
• Enforce type coercion on msg_id in a custom pre-handler that casts the value to an integer before ClipBucket processes the request

# Example nginx rule to block array-typed msg_id parameters
location ~ /private_message\.php$ {
    if ($args ~* "msg_id(\[|%5B)") {
        return 403;
    }
    if ($request_body ~* "msg_id(\[|%5B)") {
        return 403;
    }
}