CVE-2025-27088: Reflected Cross-site Scripting (XSS) in template implementation in oxyno-zeta/s3-proxy

Severity: high (CVSS 8.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2025-02-20 · updated 2026-06-17
Weakness: CWE-79

Description

oxyno-zeta/s3-proxy is an aws s3 proxy written in go. In affected versions a Reflected Cross-site Scripting (XSS) vulnerability enables attackers to create malicious URLs that, when visited, inject scripts into the web application. This can lead to session hijacking or phishing attacks on a trusted domain, posing a moderate risk to all users. It's possible to inject html elements, including scripts through the folder-list template. The affected template allows users to interact with the URL path provided by the `Request.URL.Path` variable, which is then rendered directly into the HTML without proper sanitization or escaping. This can be abused by attackers who craft a malicious URL containing injected HTML or JavaScript. When users visit such a URL, the malicious script will be executed in the user's context. This issue has been addressed in version 4.18.1 and all users are advised to upgrade. There are no known workarounds for this vulnerability.

Affected products

oxyno-zeta s3-proxy: before 2.23.1; before 4.18.1 — fixed in 2.23.1, 4.18.1

How to fix

Upgrade to a fixed version: oxyno-zeta s3-proxy 2.23.1, 4.18.1. Check the vendor advisory for mitigations.

References

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