執行摘要

A Server-Side Request Forgery (SSRF) vulnerability (CVE-2026-0745) affecting the WordPress plugin “User Language Switch” (versions ≤ 1.6.10) has been disclosed. The issue requires an authenticated administrator to supply a crafted value for the plugin’s info_language parameter. When exploited, it can cause the web server to make requests to attacker-controlled or internal/private endpoints, potentially exposing sensitive data from services on the same host or cloud metadata endpoints.

• Affected plugin: User Language Switch (≤ 1.6.10)
• 漏洞類型：伺服器端請求偽造 (SSRF)
• 所需權限：管理員
• CVSS: 5.5 (Network vector, low complexity, requires high privileges)
• CVE: CVE-2026-0745
• Mitigation status at publication: no official vendor patch available (see mitigations below)

This advisory explains SSRF, how this issue can be abused, detection and mitigation guidance, temporary hardening steps, recommended long-term fixes, and an incident response checklist written from a practical Hong Kong enterprise perspective.

What is SSRF and why it matters for WordPress sites

Server-Side Request Forgery (SSRF) happens when an attacker causes a vulnerable server-side component to make network requests on their behalf. Because requests are issued from the server itself, they bypass external network protections and can reach internal-only services or cloud metadata endpoints that are not accessible from the public internet.

In a WordPress context, SSRF is dangerous because:

• WordPress installations often share a network environment with databases, internal APIs and management endpoints.
• Cloud-hosted systems expose metadata endpoints (for example, 169.254.169.254) that may contain temporary credentials.
• If an administrator account is compromised (phishing, credential reuse, or other flaws), SSRF can be used as a powerful post-compromise tool.

Although this plugin vulnerability requires an administrator to trigger, administrative accounts are a common target—so SSRF remains a critical risk to address.

How this vulnerability works (high level, non-exact code disclosure)

The plugin exposes an endpoint that accepts an info_language parameter and makes a remote request based on that value. Input validation and destination restrictions are insufficient. A malicious administrator or an attacker with admin access can provide a URL or IP that causes the server to request:

• Internal IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16)
• Loopback addresses (127.0.0.0/8)
• Cloud metadata services (169.254.169.254)
• Internal services on privileged ports or admin APIs

This can return sensitive data to the attacker, trigger side effects on internal services, or be chained into further compromise.

現實的利用場景

• Post-compromise data exfiltration: A malicious admin injects a metadata URL. The server fetches credentials and leaks them in a response or stores them for later retrieval.
• Internal service reconnaissance: The server is used to probe internal APIs and ports, revealing lateral-movement opportunities.
• Triggering internal actions: SSRF can invoke internal endpoints that perform administrative tasks.
• Pivot to cloud keys: Metadata access in cloud environments often yields temporary credentials that allow escalation off-host.

影響評估

Although an administrator-level requirement reduces the immediate attack surface, the overall impact is meaningful:

• 機密性： Partial to full disclosure of data accessible to internal services.
• 完整性： Potential to trigger actions on internal services (e.g., job triggers), causing low-to-partial integrity impact.
• 可用性： Unlikely from simple SSRF alone, but possible if internal destructive endpoints are available.

The published CVSS vector (AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N) places this in a medium severity range. The requirement for admin privileges reduces urgency for some, but real-world incidents often chain credential compromise with SSRF to achieve larger breaches.

Immediate actions site owners should take (ordered by ease and speed)

1. 停用插件： If you use User Language Switch and cannot immediately apply a safe update, deactivate it until a vendor patch is available.
2. Rotate admin credentials and review accounts: Change passwords for all administrators; remove unknown or stale admin accounts; enforce strong, unique passwords.
3. Enforce multi-factor authentication (MFA): Require MFA for all admin logins to reduce account takeover risk.
4. Restrict admin dashboard access: Use IP allowlists, VPN, or hosting-level access controls to limit who can reach admin interfaces.
5. Block egress to sensitive IPs from the web server: At the server or cloud level, deny outbound traffic to:
   • 127.0.0.0/8
   • 10.0.0.0/8
   • 172.16.0.0/12
   • 192.168.0.0/16
   • 169.254.169.254 (cloud metadata)

   If network-level blocking is not feasible, apply application-level controls as described below.

6. Monitor logs for suspicious admin requests: Inspect admin endpoint requests (admin-ajax.php or plugin AJAX endpoints) for info_language values that look like URLs or IPs, and watch for outbound HTTP connections to private IPs.
7. Consider temporary removal or alternatives: If the plugin is critical, evaluate temporary manual solutions or trusted alternatives until a patch is available.

Technical mitigations you can implement today

Below are several options from WordPress-level fixes to server-level egress filtering and WAF rules. Apply layers appropriate for your environment.

1) WordPress-level filter: block outgoing requests to private ranges

Create a must-use plugin (mu-plugin) so it runs early and cannot be disabled through the admin UI. The snippet below prevents WordPress HTTP requests to dangerous ranges. Review and test in staging before deploying to production.

<?php
/*
Plugin Name: Block Dangerous Outbound Requests
Description: Prevents WordPress HTTP requests to private and metadata IP ranges.
Author: Security Team
*/

add_filter( 'pre_http_request', function( $preempt, $r, $url ) {
    if ( $preempt !== null ) {
        return $preempt;
    }

    $host = parse_url( $url, PHP_URL_HOST );
    if ( ! $host ) {
        return false; // Deny malformed targets
    }

    // Resolve host to IPs
    $resolved_ips = array();

    // Try DNS A/AAAA records
    $dns_records = @dns_get_record( $host, DNS_A + DNS_AAAA );
    if ( ! empty( $dns_records ) ) {
        foreach ( $dns_records as $rec ) {
            if ( ! empty( $rec['ip'] ) ) {
                $resolved_ips[] = $rec['ip'];
            } elseif ( ! empty( $rec['ipv6'] ) ) {
                $resolved_ips[] = $rec['ipv6'];
            }
        }
    }

    // Fallback to gethostbynamel
    if ( empty( $resolved_ips ) ) {
        $fallback = @gethostbynamel( $host );
        if ( ! empty( $fallback ) ) {
            $resolved_ips = $fallback;
        }
    }

    if ( empty( $resolved_ips ) ) {
        // If hostname doesn't resolve, be conservative and block
        return new WP_Error( 'blocked_outbound_request', 'Blocked outbound request: unable to resolve host safely' );
    }

    $deny_ranges = array(
        '127.0.0.0/8',
        '10.0.0.0/8',
        '172.16.0.0/12',
        '192.168.0.0/16',
        '169.254.169.254/32',
    );

    foreach ( $resolved_ips as $ip ) {
        foreach ( $deny_ranges as $range ) {
            if ( ip_in_range( $ip, $range ) ) {
                return new WP_Error( 'blocked_outbound_request', 'Blocked outbound request to private/internal address' );
            }
        }
    }

    return false; // allow request
}, 10, 3 );

/**
 * Simple IP-in-range check (supports IPv4 CIDR)
 */
function ip_in_range( $ip, $cidr ) {
    if ( strpos( $cidr, '/' ) === false ) {
        return $ip === $cidr;
    }
    list( $subnet, $bits ) = explode( '/', $cidr );
    if ( filter_var( $ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4 ) === false ) {
        // For simplicity, only handle IPv4 in this snippet
        return false;
    }
    $ip = ip2long( $ip );
    $subnet = ip2long( $subnet );
    $mask = -1 << ( 32 - (int) $bits );
    $subnet &= $mask;
    return ( $ip & $mask ) === $subnet;
}
?>

注意：

• This is intentionally conservative and may block legitimate integrations. Test before deployment.
• Place in wp-content/mu-plugins/ to ensure early loading. An attacker with file-system write access could still remove it.

2) Server-level egress blocking (strongly recommended)

Network-level outbound filtering is one of the most effective defenses. Deny outbound access from the web server to private RFC1918 ranges and cloud metadata endpoints using iptables, firewalld, or cloud security groups.

# Deny connections to metadata endpoint (example)
iptables -A OUTPUT -p tcp -d 169.254.169.254 -j REJECT

# Deny private ranges
iptables -A OUTPUT -d 10.0.0.0/8 -j REJECT
iptables -A OUTPUT -d 172.16.0.0/12 -j REJECT
iptables -A OUTPUT -d 192.168.0.0/16 -j REJECT
iptables -A OUTPUT -d 127.0.0.0/8 -j REJECT

If your application needs outbound HTTP, implement a whitelist for required destinations instead of a broad allowlist.

3) Application-layer rules (WAF / ModSecurity)

If you have a WAF or can deploy ModSecurity-style rules, block exploit attempts targeting the plugin endpoints and parameters. Examples:

# Pseudo ModSecurity rule:
SecRule REQUEST_URI "@contains admin-ajax.php" "phase:2,chain,deny,status:403,log,msg:'Potential SSRF via info_language parameter'"
  SecRule ARGS:info_language "@rx (?:https?://|//|[0-9]{1,3}\.)" "t:none"

Recommended controls:

• 阻擋請求，其中 info_language 包含 http://, https://, //, or IPv4 literals.
• Block or alert on admin endpoint calls that include URL-like values where only language codes are expected.

4) Temporary plugin-level hardening

As an emergency measure, and only if you understand the risks, you can edit the plugin to validate input. Safer approaches include adding a wrapper or mu-plugin that sanitises parameters before the plugin uses them. If editing plugin code directly, keep a backup and remember updates may overwrite changes.

Suggested constraints:

• Only accept ISO language codes (e.g., en_US); reject strings containing http, ://, slashes, colons, or numeric-only IP patterns.
• Whitelist expected values where possible.

偵測：在日誌和監控中要尋找的內容

• Access logs showing admin users accessing AJAX/plugin endpoints with info_language containing URLs or IPs.
• Outbound HTTP connections from the web server to private IP ranges or metadata addresses (check firewall, network flow, or host process logs).
• Unexpected activity on internal services that could have been triggered by the web server.
• Spikes in administrative actions associated with specific admin accounts.
• New files or changes on the filesystem following admin actions.

如果懷疑被利用，請參考事件響應檢查清單。

1. Immediately change all administrator passwords and invalidate active admin sessions.
2. 禁用易受攻擊的插件。.
3. Isolate the server at the network level (block outbound access) to prevent further exfiltration.
4. Preserve logs (web server, application, system) and take server snapshots for analysis.
5. Scan for signs of compromise: web shells, unexpected users, modified files.
6. Rotate cloud/service credentials that could have been accessed (especially if metadata access is possible).
7. Engage a qualified incident responder or forensic team if sensitive data may have been exposed.

Long-term security recommendations (beyond this vulnerability)

• Principle of least privilege: minimize admin accounts and use roles appropriately.
• 對所有特權帳戶強制執行 MFA。.
• Harden hosting: apply OS and service patches, enable process accounting, and use host-based firewalls.
• Restrict outbound connections from web servers to only necessary destinations.
• Maintain regular backups and exercise restoration procedures.
• Limit plugin footprint: install only actively maintained and reviewed plugins.
• Establish a timely update process for WordPress core, themes, and plugins.
• Use vulnerability monitoring and virtual patching from trusted providers if you require interim protection while waiting for vendor fixes.

How to test if you are vulnerable (safe testing advice)

• Do NOT perform SSRF tests against production systems or services you do not own.
• Check plugin version: verify whether "User Language Switch" is installed and if the version is ≤ 1.6.10.
• Use a staging environment to reproduce the plugin and safely observe outbound requests from the application host.
• Prefer network-level validation (egress blocking) and WAF rules to application-level active testing in production.

常見問題

Q: My site uses this plugin but I don't allow administrators except myself. Am I safe?

A: The vulnerability requires an administrator to execute. If you control admin accounts, rotate credentials, enable MFA, and apply the mitigations above. Despite restricted admin access, administrators remain attractive targets, so apply layered defenses.

Q: Will disabling outbound HTTP from the server break my site?

A: Many sites rely on outbound HTTP for legitimate services (payment gateways, remote APIs). If you block all outbound traffic, ensure whitelisting of required destinations. The safest approach is a restrictive whitelist for necessary hosts and ports.

Q: When will a vendor fix be released?

A: Plugin maintainers typically publish a patch. Update immediately when a vendor release is available. Until then, use the mitigations described above.

目前可以遵循的實用檢查清單

1. Check if "User Language Switch" is active and its version is ≤ 1.6.10.
2. If yes, either:
   • Deactivate the plugin now; or
   • Apply WAF/egress rules and harden admin access as described above.
3. Rotate admin credentials and enable MFA.
4. Consider adding the mu-plugin snippet above or applying server-level egress filters.
5. Monitor logs for requests containing info_language with suspicious values.
6. If you do not have in-house expertise, engage a qualified security professional for testing and mitigation.

來自香港安全專家的最後備註

Balancing availability and security is a daily operational reality in Hong Kong organisations and across the region. This advisory is practical: it includes immediate low-impact steps (restrict admin access, enable MFA) and stronger mitigations (egress filtering, mu-plugins, WAF rules) for those who can apply them quickly.

主要要點：

• Reduce the chance of admin compromise (MFA, least privilege).
• Reduce the impact of a compromised account (network egress controls, application-layer filters).
• Detect malicious activity early (logging, monitoring, alerting).

If you require assistance implementing these mitigations or conducting an incident investigation, engage a competent security consultant or managed security provider with experience in WordPress and cloud environments.

保持警惕。.

— 香港安全專家