Typecho 1.3.0 Pingback SSRF via X-Pingback Manipulation (CVE-2026-7025)

Executive Summary

A server-side request forgery (SSRF) vulnerability (CVE-2026-7025) has been disclosed in Typecho, a lightweight PHP blogging platform, affecting all versions up to and including 1.3.0. The flaw resides in the Service::sendPingHandle function within var/Widget/Service.php, part of the Pingback Service Endpoint. An attacker can manipulate the X-Pingback HTTP header or the link argument to forge server-side HTTP requests, potentially allowing access to internal network resources, cloud metadata endpoints, or backend services not otherwise reachable from the public internet.

CVSS Score: 7.3 (Medium)

Vulnerability Overview

Affected Products

Typecho is an open-source, lightweight blogging platform written in PHP. It supports the XML-RPC Pingback protocol, allowing other blogs and publishing platforms to notify a Typecho blog when their content links to it. The Pingback Service Endpoint processes these inbound notifications, which is where CVE-2026-7025 originates.

Technical Details

Vulnerability Root Cause

The sendPingHandle function in var/Widget/Service.php processes the X-Pingback header value and associated link parameter from inbound Pingback requests without adequately validating or restricting the destination URLs. The function uses the supplied URL to issue an outbound HTTP request from the server — creating an SSRF condition where an attacker can cause the Typecho server to fetch arbitrary URLs on their behalf.

Attack Chain

1. Attacker sends an HTTP POST request to the Typecho Pingback endpoint
   (typically /xmlrpc.php or the configured pingback URL)
 
2. The X-Pingback header or link argument is set to a
   target URL controlled by the attacker:
   - Internal IP: http://192.168.1.1/admin
   - Cloud metadata: http://169.254.169.254/latest/meta-data/
   - Internal service: http://localhost:6379/ (Redis)
   - AWS IMDS: http://169.254.169.254/latest/meta-data/iam/
 
3. Typecho's sendPingHandle function calls the URL using the
   server's own network context (inside the firewall / VPC)
 
4. The server's HTTP response is processed and may be
   reflected in the Pingback response, leaking internal data
 
5. Attacker extracts credentials, tokens, or internal service
   information from the response

SSRF via Pingback Protocol

The Pingback protocol is designed to let a remote blog server inform a local blog that it has been linked. The implementation in Typecho sends an outbound verification request to confirm the source article actually links to the target. Without URL scheme and host allowlisting, the function can be redirected to:

• Cloud metadata services — AWS IMDSv1, GCP metadata, Azure IMDS
• Internal administration panels — routers, Docker APIs, Kubernetes API
• Local services — Redis, Memcached, Elasticsearch, internal databases
• Private VPC resources — services accessible only within the deployment network

Impact Assessment

Recommendations

Immediate Actions

1. Update Typecho to the latest version once a patched release is available — check the official Typecho GitHub repository
2. Disable Pingback support if not required for your blog's functionality:
   • In Typecho admin panel, disable Pingback/Trackback settings
   • Or block access to the Pingback endpoint at the web server level
3. Apply network-level egress filtering to restrict outbound HTTP requests from the web server to only known external endpoints

Disabling Pingback in Typecho

// In your Typecho config or theme functions.php, disable pingback:
// Comment out or remove Pingback handler registration
 
// At the web server level (Nginx):
location ~ /xmlrpc.php {
    deny all;
    return 404;
}

Egress Filtering (Cloud Deployments)

Priority controls for cloud-hosted Typecho instances:
 
1. Block access to IMDSv1 (169.254.169.254) from the web server process
   - AWS: Use IMDSv2 with hop limit 1 or disable IMDSv1 at the instance level
   - GCP/Azure: Apply equivalent metadata endpoint restrictions
 
2. Apply security group / firewall rules to prevent the web server
   from initiating connections to internal RFC1918 ranges:
   10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
 
3. Use a web application firewall (WAF) rule to inspect and block
   outbound Pingback requests to private IP ranges

URL Allowlist Patch (Developer Guidance)

If patching the source directly:

// In var/Widget/Service.php - sendPingHandle function
// Add URL validation before fetching:
 
function isAllowedPingbackUrl(string $url): bool {
    $parsed = parse_url($url);
    if (!$parsed || !isset($parsed['host'])) {
        return false;
    }
    $ip = gethostbyname($parsed['host']);
    // Block RFC1918 and loopback
    if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) === false) {
        return false;
    }
    // Only allow http/https
    if (!in_array($parsed['scheme'] ?? '', ['http', 'https'])) {
        return false;
    }
    return true;
}

Detection Indicators

Example Detection Rule (ModSecurity / WAF)

# Block SSRF attempts in Pingback X-Pingback header
SecRule REQUEST_HEADERS:X-Pingback "@rx (169\.254\.|10\.|192\.168\.|172\.(1[6-9]|2[0-9]|3[01])\.|127\.0\.0\.1|localhost)" \
    "id:9102026,\
    phase:2,\
    deny,\
    status:403,\
    msg:'CVE-2026-7025 Typecho SSRF Attempt via X-Pingback',\
    logdata:'Matched Data: %{MATCHED_VAR} found within %{MATCHED_VAR_NAME}'"

Post-Remediation Checklist

1. Verify Typecho version — confirm upgraded version is beyond 1.3.0 once patch is available
2. Audit web server egress logs for any historical requests to internal IP ranges from the Pingback handler
3. Rotate cloud credentials if the server runs on AWS/GCP/Azure and may have been exploited — assume IMDSv1 tokens were accessible
4. Review internal service exposure — audit which internal services accept unauthenticated connections reachable from the web server
5. Enable IMDSv2 on all cloud instances hosting PHP applications to mitigate metadata SSRF impact

References

• NIST NVD — CVE-2026-7025
• Typecho GitHub Repository
• CWE-918: Server-Side Request Forgery
• OWASP SSRF Prevention Cheat Sheet