CVE-2025-63938 identifies an integer overflow vulnerability in Tinyproxy, an open-source HTTP proxy server, affecting versions through 1.11.2. The flaw resides in the strip_return_port() function within the source file src/reqs.c. Integer overflow occurs when an arithmetic operation attempts to create a numeric value outside the range that can be represented with a given number of bits, potentially causing unexpected behavior such as buffer overflows or memory corruption. In this context, the overflow could lead to improper handling of port stripping from HTTP requests, which may be exploited by an attacker to manipulate memory or cause a denial of service. Although no exploits have been reported in the wild, the vulnerability's presence in a network-facing proxy service increases its risk profile. Tinyproxy is commonly deployed to relay HTTP traffic, often in environments requiring lightweight proxy solutions. The absence of a CVSS score and official patches indicates this is a newly disclosed vulnerability, with mitigation relying on forthcoming updates or manual code review and patching. The vulnerability's exploitation could compromise confidentiality, integrity, or availability of network communications passing through the proxy, depending on the attacker's goals and environment.

For European organizations, the impact of CVE-2025-63938 could be significant, especially for those using Tinyproxy in critical network infrastructure, such as ISPs, enterprises, or government agencies. Exploitation could lead to denial of service, disrupting access to web resources or internal services. In worst-case scenarios, memory corruption might allow remote code execution, potentially enabling attackers to pivot within networks or exfiltrate sensitive data. Given the proxy's role in managing HTTP traffic, confidentiality and integrity of communications could be compromised. Organizations with regulatory requirements around data protection (e.g., GDPR) may face compliance risks if the vulnerability is exploited. The lack of known exploits currently reduces immediate risk, but the potential for future weaponization necessitates proactive measures. The impact is heightened in sectors with critical infrastructure or high-value targets, including finance, telecommunications, and government.

To mitigate CVE-2025-63938, organizations should first inventory their use of Tinyproxy and identify affected versions (up to 1.11.2). Until official patches are released, consider applying temporary workarounds such as disabling or restricting access to vulnerable proxy instances, especially from untrusted networks. Network segmentation can limit exposure. Monitoring proxy logs for unusual activity or malformed requests targeting port stripping functionality can provide early detection. Engage with the Tinyproxy community or maintainers to obtain patches or backported fixes as soon as they become available. Where possible, conduct code audits or implement input validation enhancements around the strip_return_port() function to prevent integer overflow conditions. Additionally, consider deploying web application firewalls (WAFs) or intrusion prevention systems (IPS) with rules to detect and block exploit attempts targeting this vulnerability. Finally, maintain robust incident response plans to quickly address any exploitation attempts.