Introduction to CVE-2022-3590
WordPress is one of the most widely used content management systems globally. It is extensively used for blogs, business websites, and e-commerce platforms. Because of its widespread adoption, it is frequently targeted by both security researchers and cybercriminals. A significant vulnerability that affected WordPress Core was CVE-2022-3590, which involved unauthenticated blind Server-Side Request Forgery (SSRF).
This flaw allowed attackers to forge server-side requests without providing any credentials. Although the issue was resolved by the WordPress development team, it remains important to understand how it worked and what it means for website security.
What is SSRF in Cybersecurity?
SSRF stands for Server-Side Request Forgery. An SSRF attack involves exploiting a web server to send requests on behalf of the attacker to internal or external destinations the attacker would not normally be able to reach directly.
Under normal circumstances, a web server communicates only with trusted systems. In an SSRF attack, however, attackers manipulate the server into connecting to internal services, cloud metadata endpoints, private APIs, or other restricted resources that are not accessible from the public internet.
Understanding Blind SSRF Vulnerabilities
A blind SSRF vulnerability is one where the attacker cannot directly observe the server’s response after sending an exploitative request. Because there is no visible output, attackers must rely on indirect methods to determine whether the request was successfully executed.
A common technique is to set up an external listening server and check whether the targeted website attempts to connect to it. Tools such as Burp Collaborator or DNS callback services are often used for this purpose. Even without a visible response, attackers can gather useful information about the internal environment of a vulnerable system through these out-of-band techniques.
What Does Unauthenticated Mean?
An unauthenticated vulnerability means that an attacker does not need to log in or hold any valid credentials before attempting the attack. This significantly increases the severity of the issue because the attack surface expands to anyone on the internet, not just users who already have access to the system.
Unauthenticated attacks are generally considered higher risk than authenticated ones because they remove the barrier of needing prior access, making exploitation far more accessible to a wider range of threat actors.
How CVE-2022-3590 Works in WordPress
CVE-2022-3590 exploited weaknesses in how WordPress processed certain outbound requests, specifically within the Pingback and XML-RPC feature. The underlying issue was insufficient validation inside the wp_http_validate_url() function, which failed to block requests directed at private, loopback, or reserved IP address ranges.
Because the flaw was a blind SSRF, it did not make it any less harmful. In environments with weak network protection, attackers could trigger requests to internal IP addresses, localhost, or cloud metadata services without the site administrators’ knowledge.
Which WordPress Versions Were Affected?
CVE-2022-3590 affected all versions of WordPress Core up to and including version 6.0.2. The vulnerability was patched in WordPress 6.0.3, released in October 2022. Website administrators running any version prior to 6.0.3 were at risk, particularly those whose hosting environment lacked strict network isolation or outbound request filtering.
Updating to WordPress 6.0.3 or any later release addresses this specific vulnerability. Staying current with all future updates remains equally important.
Why This Vulnerability Was Dangerous
The risk posed by CVE-2022-3590 stemmed from the ability to reach internal resources through the affected server. Many organisations rely on firewalls and network isolation to protect internal servers from external access. SSRF attacks are capable of bypassing these defences because the requests appear to originate from a trusted server rather than from an external attacker.
This attack vector was particularly dangerous in cloud-hosted environments, where internal metadata services store sensitive information such as temporary credentials and configuration details.
How Attackers Exploit SSRF Vulnerabilities
An attacker typically exploits an SSRF vulnerability by supplying a maliciously crafted URL to the vulnerable request handler. The server then sends requests to whatever destinations the attacker specifies. These destinations can include internal API endpoints, private dashboards, cloud service metadata URLs, or other devices on the same internal network as the server.
In some cases, SSRF can also be used for internal network reconnaissance, allowing attackers to map out services that are not directly reachable from the internet.
Internal Server Request Attacks Explained
An internal server request cyber attack involves making the server communicate with resources on its own internal network. These resources are typically protected by firewalls and are not accessible from the public internet.
For example, an attacker may instruct the server to send a request to:
http://127.0.0.1/
or to the AWS EC2 instance metadata service:
http://169.254.169.254/
These internal endpoints may reveal configuration details, temporary access tokens, or system information that can be used to further compromise the environment.
Real Security Risks of CVE-2022-3590
The actual impact of CVE-2022-3590 depended heavily on the hosting environment and server configuration. In poorly secured environments, attackers could use this SSRF flaw to scan internal systems or access sensitive data.
Potential risks included:
- Internal network discovery and service enumeration
- Access to cloud metadata endpoints and temporary credentials
- Exposure of hidden or restricted internal services
- Credential leakage from cloud configuration stores
- Firewall bypass using the server as a proxy
Although not every vulnerable website could be fully compromised through this flaw alone, SSRF vulnerabilities significantly increase the overall attack potential, particularly when combined with other weaknesses.
Can SSRF Lead to Data Leakage?
Yes, data leakage can result from SSRF vulnerabilities. If attackers successfully reach internal services or cloud metadata endpoints, they may obtain configuration details, session tokens, or temporary credentials. Cloud providers commonly use metadata services to deliver short-lived credentials to hosted instances. If these endpoints become reachable through an SSRF flaw, attackers may be able to access cloud resources using those stolen credentials.
Example of an SSRF Attack Scenario
Consider a WordPress website hosted on a cloud server. An attacker identifies the SSRF vulnerability and supplies a maliciously crafted URL targeting the cloud provider’s metadata service at http://169.254.169.254/. The server processes the request and connects to the metadata endpoint. If the response is returned or logged anywhere accessible, the attacker may retrieve temporary credentials or configuration details, potentially escalating their access to other cloud resources.
Even in a blind SSRF scenario where no response is directly visible, attackers can use DNS callbacks or external request loggers to confirm that the server made the request, and then work from there.
How WordPress Mitigated CVE-2022-3590
WordPress developers resolved this issue in version 6.0.3 by patching the wp_http_validate_url() function. The fix introduced stricter validation rules that block outbound requests directed at loopback addresses, private IP ranges, and reserved IP address spaces. This prevents the server from being used as a proxy to reach internal or restricted destinations.
Website administrators were strongly advised to update to version 6.0.3 as soon as it became available.
Security Improvements Introduced by WordPress
Following the discovery of CVE-2022-3590, WordPress strengthened its request handling and URL validation logic. The updates improved protection against unauthorised internal requests and tightened handling of potentially harmful URL schemes. These changes made WordPress Core more resilient against similar SSRF vulnerabilities going forward.
How to Protect Your WordPress Website from SSRF
Protecting a WordPress site against SSRF attacks requires both application-level and server-level security measures. Administrators should ensure they are running the latest version of WordPress at all times. They should also avoid using outdated plugins and themes, as unmaintained components can introduce separate vulnerabilities. Implementing a web application firewall and enabling security plugins that monitor outbound requests can provide an additional layer of protection.
Best WordPress Security Practices
Strong security practices are essential for preventing vulnerabilities from escalating. Website administrators should use strong passwords, enable two-factor authentication, perform regular backups, and limit administrator access to trusted individuals only. Regular security audits and vulnerability scans also help identify weaknesses before they can be exploited.
Importance of Secure WordPress Hosting
Secure WordPress hosting plays an important role in protecting websites against modern cyber threats. A well-configured hosting environment can reduce the risks posed by SSRF attacks through measures such as firewalls, network segmentation, outbound request filtering, and real-time monitoring. Many reputable hosting providers offer features including malware detection, DDoS protection, intrusion detection systems, and automated security updates.
Why Keeping WordPress Updated is Important
Outdated versions of WordPress remain one of the most common causes of website compromises. Attackers regularly scan for sites running older versions because publicly documented exploit techniques are straightforward to apply. Administrators should update their WordPress installation as soon as new releases become available. Each update brings bug fixes, security patches, and performance improvements that reduce overall exposure.
Recommended Security Plugins for WordPress
Several types of security plugins help make WordPress installations more resistant to vulnerabilities and malicious attacks. These plugins typically offer firewall protection, malware scanning, login security, and brute force attack prevention. Administrators should choose well-maintained plugins with a strong update history. Used alongside secure hosting and regular maintenance, these plugins contribute to a layered and more robust WordPress security posture.
Conclusion
CVE-2022-3590 demonstrated the real-world impact that SSRF vulnerabilities can have on widely used platforms like WordPress. By exploiting the Pingback and XML-RPC feature and a weakness in the wp_http_validate_url() function, attackers could trigger unauthorised server-side requests without any authentication. The vulnerability affected all WordPress Core versions up to and including 6.0.2 and was resolved in the 6.0.3 security release.
The incident underlines the importance of validating all outbound requests, keeping software up to date, and securing the server environment. Regular updates, strong hosting configurations, and layered security practices remain the most effective defences against this class of vulnerability.