CVE-2022-23644 is a Server-Side Request Forgery (SSRF) vulnerability identified in BookWyrm, a decentralized social network platform designed for tracking reading habits and reviewing books. The vulnerability exists in the functionality that allows the platform to load book cover images via URLs. Specifically, any BookWyrm instance running a version prior to 0.3.0 is susceptible to SSRF attacks initiated by authenticated users. SSRF vulnerabilities occur when an attacker can manipulate a server to make unintended HTTP requests, potentially accessing internal or protected resources that are not directly reachable from the attacker’s network. In this case, a logged-in user can craft malicious URLs that the server will fetch, enabling the attacker to probe internal networks, access sensitive metadata, or interact with internal services that are otherwise inaccessible externally. The vulnerability was patched in version 0.3.0 of BookWyrm. Until systems are upgraded, administrators are advised to restrict registration and limit membership to trusted users to reduce the attack surface. There are no known exploits in the wild as of the published date, and no public proof-of-concept exploits have been reported. The vulnerability is classified under CWE-918, which covers SSRF issues. The attack requires authentication, meaning only logged-in users can exploit it, which somewhat limits the exposure but does not eliminate risk, especially in open or semi-open communities. The potential for internal network reconnaissance or exploitation of internal services makes this vulnerability significant for organizations hosting BookWyrm instances.

For European organizations running BookWyrm instances, especially those with open or semi-open registration policies, this SSRF vulnerability poses a risk to internal network security and data confidentiality. Attackers exploiting this flaw could access internal services, potentially leading to information disclosure, lateral movement, or further exploitation within the network. Given that BookWyrm is a niche social platform, the direct impact may be limited to organizations or communities actively using it. However, if BookWyrm is deployed within academic, cultural, or library institutions, which are common in Europe, the compromise could lead to exposure of sensitive internal resources or user data. The requirement for authenticated access reduces the risk from anonymous attackers but does not eliminate insider threats or attacks from compromised accounts. Additionally, SSRF can be leveraged as a pivot point for more extensive network intrusions if internal services are vulnerable. The decentralized nature of BookWyrm means that many independent instances exist, potentially with varying security postures, increasing the risk that some instances remain vulnerable. The impact on availability is likely low, but confidentiality and integrity of internal systems could be compromised depending on the attacker’s objectives and network architecture.

1. Immediate upgrade of all BookWyrm instances to version 0.3.0 or later to apply the official patch addressing the SSRF vulnerability. 2. Until patching is complete, restrict user registration to trusted individuals only, effectively limiting the pool of authenticated users who can exploit the vulnerability. 3. Implement network segmentation and firewall rules to restrict the BookWyrm server’s outbound HTTP requests to only trusted external endpoints, preventing arbitrary internal network access via SSRF. 4. Monitor server logs for unusual outbound requests or patterns indicative of SSRF exploitation attempts, such as requests to internal IP ranges or unexpected services. 5. Conduct regular security audits of BookWyrm instances and underlying infrastructure to identify and remediate any additional vulnerabilities or misconfigurations. 6. Educate administrators and users about the risks of SSRF and encourage strong authentication and account monitoring to detect compromised accounts. 7. Consider deploying Web Application Firewalls (WAFs) with rules to detect and block SSRF attack patterns targeting the cover image URL functionality. 8. Review and harden internal services that could be targeted via SSRF to minimize the potential impact if exploited.