CVE-2025-27220 is a vulnerability classified under CWE-1333, indicating inefficient regular expression complexity leading to a ReDoS attack vector. The flaw exists in the ruby-lang CGI gem, specifically in the Util#escapeElement method, which uses a regular expression that can be exploited by an attacker to cause excessive backtracking. When maliciously crafted input is processed by this method, the regular expression engine consumes disproportionate CPU resources, potentially leading to denial of service by exhausting server processing capacity. The affected versions are all releases prior to 0.4.2, including 0, 0.3.6, and 0.4.0. The vulnerability is remotely exploitable without authentication or user interaction, but the attack complexity is high due to the need to craft specific input patterns that trigger the inefficient regex behavior. The CVSS 3.1 vector (AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L) reflects network attack vector, high attack complexity, no privileges or user interaction required, scope changed, no confidentiality or integrity impact, and low availability impact. No public exploits have been reported yet, but the vulnerability poses a risk to web applications relying on the CGI gem for input escaping. The issue was published on March 3, 2025, and no official patches are linked in the provided data, but upgrading to version 0.4.2 or later is recommended to remediate the vulnerability.

For European organizations, the primary impact of CVE-2025-27220 is the potential for denial of service conditions in web applications that utilize the vulnerable ruby-lang CGI gem versions. This can lead to service outages, degraded user experience, and potential loss of business continuity. Since the vulnerability affects availability only, confidentiality and integrity remain intact. However, availability disruptions can have cascading effects on customer trust and operational efficiency, especially for critical services such as e-commerce platforms, government portals, and financial applications. Organizations with high traffic or those exposed to the internet are at greater risk. The medium severity rating suggests that while the threat is not critical, it should not be ignored, particularly in environments where uptime is essential. Additionally, the changed scope in the CVSS vector indicates that the vulnerability could affect components beyond the immediate CGI gem context, potentially impacting dependent systems or services.

1. Upgrade the ruby-lang CGI gem to version 0.4.2 or later where the vulnerability is resolved. 2. Implement strict input validation to reject or sanitize inputs that could trigger the vulnerable regular expression, focusing on patterns known to cause excessive backtracking. 3. Employ rate limiting and request throttling on endpoints using the CGI gem to reduce the risk of resource exhaustion from repeated malicious requests. 4. Monitor application performance and logs for unusual spikes in CPU usage or request patterns indicative of ReDoS attempts. 5. Consider deploying Web Application Firewalls (WAFs) with custom rules to detect and block suspicious input patterns targeting the vulnerable method. 6. Conduct regular dependency audits and vulnerability scans to ensure all Ruby gems are up to date and free from known vulnerabilities. 7. Educate development teams about secure coding practices related to regular expressions and input handling to prevent similar issues in future code.