CVE-2025-63938 identifies an integer overflow vulnerability in Tinyproxy, a widely used lightweight HTTP proxy server, affecting versions up to 1.11.2. The vulnerability exists in the strip_return_port() function located in src/reqs.c, where improper handling of integer values can lead to an overflow condition (CWE-190). This flaw can be triggered remotely without authentication or user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:N/UI:N). The overflow may allow an attacker to manipulate internal proxy request processing, potentially leaking sensitive information (confidentiality impact) or altering data (integrity impact). However, the vulnerability does not affect system availability. The CVSS score of 6.5 reflects a medium severity level, balancing the ease of exploitation with limited impact scope. No patches or exploits are currently documented, indicating that the vulnerability is newly disclosed and not yet weaponized. Tinyproxy’s role as a proxy server means that compromised instances could be used to intercept or modify HTTP traffic, posing risks to organizations relying on it for secure communications. The vulnerability’s presence in an open-source project underscores the need for timely updates and monitoring. Given the lack of authentication requirements and no user interaction needed, exploitation could be automated, increasing risk if exposed to untrusted networks.

For European organizations, the integer overflow in Tinyproxy could lead to unauthorized disclosure of sensitive information passing through the proxy or unauthorized modification of HTTP requests and responses, undermining data confidentiality and integrity. Sectors such as finance, government, and telecommunications that rely on proxy servers for secure and controlled internet access are particularly at risk. While availability is not directly impacted, the breach of confidentiality or integrity could facilitate further attacks, including data exfiltration or man-in-the-middle scenarios. Organizations using Tinyproxy in perimeter defenses or internal network segments may inadvertently expose critical data flows. The absence of known exploits currently reduces immediate risk, but the medium severity rating and ease of exploitation without authentication necessitate proactive measures. Failure to address this vulnerability could lead to compliance issues under GDPR if personal data is compromised. Additionally, the vulnerability could be leveraged as a foothold for lateral movement within networks, amplifying its impact.

Organizations should immediately inventory their use of Tinyproxy and identify any instances running version 1.11.2 or earlier. Although no official patch is currently available, monitoring the Tinyproxy project for updates or security advisories is critical. In the interim, restrict network access to Tinyproxy instances, limiting exposure to trusted networks only. Employ network segmentation and firewall rules to prevent unauthorized external access to proxy services. Implement strict logging and monitoring of proxy traffic to detect anomalous behavior indicative of exploitation attempts. Consider deploying Web Application Firewalls (WAFs) or Intrusion Detection Systems (IDS) with signatures tuned for proxy anomalies. Where feasible, replace Tinyproxy with alternative proxy solutions that have active security support. Conduct regular security assessments and penetration tests focusing on proxy infrastructure. Finally, educate IT staff about this vulnerability to ensure rapid response once patches become available.