S3-Proxy allows Reflected Cross-site Scripting (XSS) in template implementation

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

8.4 · 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 · score source

EPSS

• CVE-2025-27088: 0.50% estimated exploitation activity in the next 30 days; percentile 42.66 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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 high risk to all users. Details Give all details on the vulnerability. Pointing to the incriminated source code is very helpful for the maintainer. It's possible to inject html elements, including scripts through the folder-list template. It seems like the .Request.URL.Path variable is not escaped. I did some research and found it might be due to the text/template import being used in the template implementation, instead of the safer html/template. PoC Complete instructions, including specific configuration details, to reproduce the vulnerability. Using the default template configuration, the vulnerability can be reproduced with the following steps. 1. Navigate to https://your-s3-proxy.com/path-not-found and confirm the page looks as…

Published by the source

20 Feb 2025, 22:18 UTC

Last modified by the source

21 Feb 2025, 16:10 UTC

Source last checked

26 Oct 2026, 15:08 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-pp9m-qf39-hxjc

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# Patch Next advisory brief: CVE-2025-27088

Advisory: S3-Proxy allows Reflected Cross-site Scripting (XSS) in template implementation
IDs: CVE-2025-27088, GHSA-pp9m-qf39-hxjc
Record: https://patchnext.com/advisories/cve-2025-27088 (revision 1, source checked 26 Oct 2026, 15:08 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/oxyno-zeta/s3-proxy/cmd/s3-proxy 0.0.0-20250220214310-c611c741ed48. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/oxyno-zeta/s3-proxy/cmd/s3-proxy: affected <= 0.0.0-20250212215955-2873011f7c42; fixed in 0.0.0-20250220214310-c611c741ed48

## Suggested inspection (read-only)
- Go github.com/oxyno-zeta/s3-proxy/cmd/s3-proxy: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/oxyno-zeta/s3-proxy/cmd/s3-proxy.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-pp9m-qf39-hxjc (GitHub-reviewed advisory GHSA-pp9m-qf39-hxjc lists affected ranges: Go github.com/oxyno-zeta/s3-proxy/cmd/s3-proxy >=0 <=0.0.0-20250212215955-2873011f7c42)

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