CVE-2025-27088 is a high-severity reflected cross-site scripting (XSS) vulnerability present in the oxyno-zeta s3-proxy, an AWS S3 proxy written in Go. This vulnerability allows attackers to create malicious URLs that, when visited, inject scripts into the web application. The risk is particularly concerning as it can lead to session hijacking or phishing attacks on a trusted domain, affecting all users of the application. It is critical for organizations using this software to understand the implications of this vulnerability and take immediate action.
The vulnerability is due to improper sanitization of user input in the folder-list template, which allows the `Request.URL.Path` variable to be rendered directly into HTML. Attackers can exploit this by crafting URLs that include injected HTML or JavaScript. When users access these malicious URLs, the injected scripts will execute within the user's context, compromising their session and potentially leading to unauthorized access.
This issue has been addressed in version 4.18.1 of the s3-proxy, and all users are strongly advised to upgrade to this version as soon as possible. There are currently no known workarounds to mitigate this vulnerability.
Organizations should prioritize patching immediately to reduce the risk associated with this vulnerability.
Vulnerability Details
The vulnerability is classified as CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'). The CVSS score is 8.4, indicating a high severity level. The affected product is oxyno-zeta's s3-proxy, specifically versions prior to 4.18.1. The vulnerability was published on February 20, 2025.
Technical Analysis
The root cause of this vulnerability lies in the failure to properly sanitize user-supplied input in the folder-list template. The attack vector is network-based, with a low attack complexity, meaning that an attacker does not require any special privileges to exploit it. User interaction is required, as the malicious URL must be visited by the victim.
The implications of this vulnerability are significant. The confidentiality impact is rated as high, as attackers can gain access to sensitive user information, while the integrity impact is rated as none. The availability impact is also none, as the vulnerability does not affect the availability of the application itself.
Risk & Impact Analysis
The risk to organizations includes potential session hijacking and phishing attacks, which can have far-reaching consequences. Attackers may leverage this vulnerability to impersonate users or gain unauthorized access to sensitive information. The blast radius of this vulnerability is widespread, affecting all users of the affected application.
Given the high CVSS score and the potential for exploitation, organizations should address this vulnerability in their priority patch cycle. The urgency is underscored by the lack of known workarounds.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The affected versions of the s3-proxy include all versions prior to 4.18.1. Users are encouraged to upgrade to this version to mitigate the vulnerabilities.
Mitigation & Remediation
To mitigate the risk associated with this vulnerability, organizations should upgrade to version 4.18.1 of the s3-proxy. If an immediate upgrade is not feasible, organizations should implement strict input validation and output encoding, although no effective workarounds are currently known. Continuous security testing can help identify similar vulnerabilities in the future. For more information on effective strategies for remediation, see our penetration testing services.
Detection Guidance
Organizations should monitor logs for unusual patterns of user activity that may indicate attempts to exploit this vulnerability. Behavioral anomalies such as unexpected redirects or script executions should also be flagged. Network signatures that identify requests containing suspicious URL parameters can help in early detection.
AppSecure Threat Intelligence Insight
The long-term significance of CVE-2025-27088 highlights the importance of input validation in web applications. This vulnerability serves as a reminder of the potential risks associated with XSS and the need for robust security practices in software development. Security teams should conduct regular audits and implement comprehensive testing strategies to ensure vulnerabilities are identified and remediated promptly. For further reading, refer to our articles on web application security testing and penetration testing methodology best practices.
Finally, organizations should continuously assess their security posture to adapt to evolving threats and vulnerabilities.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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