CVE-2023-54357: Joomla com_booking Unauthenticated User Enumeration Vulnerability

Technical summary

CVE-2023-54357 is an unauthenticated information disclosure vulnerability in the Joomla com_booking component (version 2.4.9) arising from improper access controls on the getUserData function within the customer controller. The vulnerability permits attackers to retrieve sensitive user profile data—including usernames, user display names, and email addresses—by sending GET requests to index.php with parameters option=com_booking, controller=customer, task=getUserData, and a numeric id parameter. The lack of authentication checks and absence of rate limiting or enumeration protections allow brute-force iteration over user IDs to systematically extract account information. The issue is classified under CWE-203 (Observable Discrepancy), reflecting the information leakage through response differentials or accessible data fields.

Business impact

User enumeration attacks enable threat actors to build targeted contact lists for phishing, social engineering, and credential stuffing campaigns. Email addresses and usernames harvested from your Joomla installation become initial targets for account takeover attempts. Organizations running e-commerce, booking, or membership sites with the com_booking extension face elevated risk of account compromise, especially if users reuse credentials across systems. The absence of authentication requirements means the attack surface is maximized—any internet user can conduct reconnaissance at scale. For multi-tenant or SaaS environments, this leakage may expose customer data across multiple organizations. Reputational harm and potential regulatory exposure (GDPR, CCPA) may follow if user data harvesting is discovered.

Affected systems

Joomla installations running com_booking component version 2.4.9 are directly affected. The vulnerability applies only to this specific version; confirm your deployment version in the component configuration or via direct file inspection (check the component's manifest or version constant). Joomla sites with the booking component enabled and accessible via standard URL routing (index.php?option=com_booking) are exploitable. Environments with restrictive web server configurations, URL rewriting that blocks parameter-based access, or firewall rules blocking external enumeration requests may have reduced exposure, but these are defense-in-depth measures, not true mitigations.

Exploitability

Exploitability is straightforward and does not require advanced technical skill. An attacker needs only basic HTTP client capabilities (curl, a browser, or a simple script) and no authentication. The attack can be fully automated to enumerate hundreds or thousands of user IDs in minutes. The CVSS 3.1 score of 7.5 (HIGH) reflects the network-based attack vector, low complexity, no privilege or user interaction requirements, and high confidentiality impact. The lack of integrity or availability impact (users are not modified or locked out) prevents a critical rating, but the unrestricted reconnaissance capability and minimal attacker effort make this a priority issue. Exploit code or proof-of-concept tools are trivial to construct and likely already circulating; assume active exploitation in hostile networks.

Remediation

Immediate action is required: update the com_booking component to a patched version released after 2.4.9. Contact the component vendor or review the official Joomla extensions directory for the latest available release. Verify patch availability and changelog notes to confirm the information disclosure flaw is resolved before deploying. As an interim measure (not a substitute for patching), implement web application firewall (WAF) rules to detect and block requests matching the pattern option=com_booking&controller=customer&task=getUserData with numeric id parameters. Disable or uninstall the com_booking component entirely if it is not actively used. Rotate email addresses and usernames if they were generated during development or testing, and monitor for unusual login attempts on affected accounts.

Patch guidance

Upgrade the com_booking component to the first available version after 2.4.9 that includes a security fix for this vulnerability. Consult the official Joomla component vendor's security advisories or release notes to identify the correct target version and any conditional dependencies. Test the patch in a staging environment before production deployment to ensure no functional regressions or compatibility issues with your Joomla core version and other installed extensions. After patching, verify the getUserData endpoint is no longer accessible via unauthenticated requests by attempting a test call; a proper fix should return an error or redirect rather than user data.

Detection guidance

Monitor web server access logs for GET requests to index.php containing the parameters option=com_booking, controller=customer, and task=getUserData with varying numeric id values in rapid succession. Detection patterns: sequential or high-frequency id parameter changes (e.g., id=1, id=2, id=3 within seconds) from a single IP address indicate enumeration activity. Enable and review Joomla's access control logging to identify failed or suspicious getUserData calls. Deploy a WAF with rules that flag or block suspicious parameter combinations or request rates targeting this endpoint. Correlate log events with geographic intelligence or threat feeds to identify if enumeration activity aligns with known bad actors. Set up alerts for any successful information disclosures from getUserData if you can parse response payloads.

Why prioritize this

This vulnerability merits high prioritization due to its trivial exploitability, lack of authentication requirement, and immediate business impact on account security posture. User enumeration is a reconnaissance precursor to credential attacks and phishing campaigns, making it a force multiplier for downstream compromise. The HIGH CVSS score reflects the severity, and the broad exposure (any internet-accessible Joomla site running the vulnerable component) means the risk landscape is wide. Unlike vulnerabilities requiring specialized knowledge or elevated privileges, this flaw can be weaponized by attackers of any skill level. Rapid patching is essential before organized threat actors add enumeration to their reconnaissance playbooks.

Risk score, explained

The CVSS 3.1 score of 7.5 (HIGH) is derived from: Network-based attack vector (AV:N) – requires no local access; Low attack complexity (AC:L) – no special conditions or user interaction; No privilege requirements (PR:N) and no user interaction (UI:N) – fully unauthenticated and automatic; Unchanged scope (S:U) – impact confined to the affected system; High confidentiality impact (C:H) – user account identifiers and contact information are disclosed; No integrity (I:N) or availability impact (A:N) – data is only read, not modified or service disrupted. The HIGH severity reflects that confidentiality of user data is significantly compromised, though the absence of integrity or availability damage prevents a CRITICAL rating. Organizations must treat this as a near-critical issue in their patch cycle.

Frequently asked questions