CVE-2021-47954 Overview
CVE-2021-47954 is a SQL injection vulnerability in LayerBB 1.1.4, an open-source forum software package. The flaw exists in the search_query parameter handled by /search.php. An unauthenticated attacker can send a crafted POST request containing malicious SQL syntax, such as CASE WHEN expressions, to manipulate backend database queries. Successful exploitation allows extraction of sensitive data from the underlying database, including user credentials and configuration values. The issue is classified under CWE-89: Improper Neutralization of Special Elements used in an SQL Command.
Critical Impact
Unauthenticated attackers can extract arbitrary data from the LayerBB database over the network with no user interaction required.
Affected Products
- LayerBB 1.1.4
- LayerBB forum installations exposing /search.php
- Deployments without input sanitization patches applied
Discovery Timeline
- 2026-05-16 - CVE-2021-47954 published to NVD
- 2026-05-18 - Last updated in NVD database
Technical Details for CVE-2021-47954
Vulnerability Analysis
The vulnerability resides in the search functionality of LayerBB 1.1.4. The /search.php endpoint accepts a search_query parameter via POST and incorporates the value into a SQL statement without adequate sanitization or parameterization. Attackers inject SQL syntax that alters the structure of the executed query.
Public exploitation references demonstrate the use of conditional CASE WHEN expressions to perform boolean-based blind SQL injection. The attacker compares database values character-by-character and observes response differences to exfiltrate data. Because the endpoint does not require authentication, the attack surface is exposed to any network-reachable client.
The vulnerability falls under [CWE-89] and reflects a failure to neutralize special characters before passing user-controlled input to the SQL interpreter. Technical proof-of-concept details are documented in Exploit-DB #49593 and the VulnCheck Advisory on SQL Injection.
Root Cause
The root cause is direct concatenation of unsanitized user input from the search_query POST parameter into a SQL query string. LayerBB 1.1.4 does not use prepared statements or parameter binding for this query path, allowing injected SQL fragments to be parsed and executed by the database engine.
Attack Vector
The attack vector is network-based. An attacker sends an HTTP POST request to /search.php with a malicious search_query value containing SQL injection payloads. No credentials, user interaction, or local access are required. The vulnerability can be exploited against any internet-exposed LayerBB 1.1.4 installation.
No verified code examples are available. See the Exploit-DB #49593 entry for technical proof-of-concept details.
Detection Methods for CVE-2021-47954
Indicators of Compromise
- POST requests to /search.php containing SQL keywords such as CASE, WHEN, SELECT, UNION, or SLEEP in the search_query parameter
- Unusual response time variance from /search.php consistent with time-based blind SQL injection
- Web server access logs showing repeated automated requests against /search.php from a single source
- Database error messages referencing the LayerBB search query in application logs
Detection Strategies
- Deploy web application firewall (WAF) rules to flag SQL metacharacters and boolean injection patterns in the search_query parameter
- Inspect application logs for query failures or syntax errors originating from search functionality
- Correlate authentication anomalies and credential reuse with prior /search.php request patterns
Monitoring Recommendations
- Enable verbose logging on the LayerBB web server and database to capture full request bodies for /search.php
- Monitor outbound database query volume and patterns for anomalous SELECT activity against user tables
- Alert on requests to /search.php from non-browser user agents or scripted clients
How to Mitigate CVE-2021-47954
Immediate Actions Required
- Restrict public access to LayerBB /search.php until input validation is in place, using IP allowlisting or authentication gating at the reverse proxy
- Deploy WAF signatures that block SQL injection payloads targeting the search_query parameter
- Audit the database for unauthorized read activity and rotate credentials stored in the affected LayerBB instance
Patch Information
No official vendor patch URL is referenced in the available CVE data. Administrators should consult the VulnCheck Advisory on SQL Injection for remediation guidance and consider migrating to a maintained forum platform if upstream fixes are not available.
Workarounds
- Modify the application code to use parameterized queries or prepared statements for all database calls involving search_query
- Apply server-side input validation that rejects non-alphanumeric characters in search submissions
- Place LayerBB behind an authenticating reverse proxy to limit exposure of the search endpoint to trusted users
# Example WAF rule (ModSecurity) to block SQL keywords in search_query
SecRule ARGS:search_query "@rx (?i)(union(\s)+select|case(\s)+when|sleep\(|benchmark\()" \
"id:1004794,phase:2,deny,status:403,msg:'CVE-2021-47954 LayerBB SQLi attempt blocked'"
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
