GHSA-pp9m-qf39-hxjc
S3-Proxy allows Reflected Cross-site Scripting (XSS) in template implementation
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
github.com/oxyno-zeta/s3-proxy/cmd/s3-proxyReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
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.
-
Navigate to
https://your-s3-proxy.com/path-not-foundand confirm the page looks as follows: -
Try inserting an HTML element by changing
/path-not-foundto/<img src="x">and confirm the page looks as follows: -
Now it should be possible to run any JavaScript by manipulating the
onerrorproperty of the img element. This should make the link look likehttps://your-s3-proxy.com/<img src="x" onerror="alert(1)">. Confirm that going to this URL will in fact shows an alert in the browser.
Impact
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, leading to potential risks such as:
- Session Hijacking: Malicious scripts could be used to steal session cookies or other sensitive information.
- Phishing Attacks: JavaScript could be injected to trick users into submitting sensitive information, such as login credentials.
This vulnerability can be exploited by attackers who craft URLs containing malicious payloads, which would then execute in the user's browser when they access the affected page. This poses a high risk to all users who visit such URLs.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/oxyno-zeta/s3-proxy/cmd/s3-proxy | all versions | 0.0.0-20250220214310-c611c741ed48 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/oxyno-zeta/s3-proxy/cmd/s3-proxy. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/oxyno-zeta/s3-proxy/cmd/s3-proxy to 0.0.0-20250220214310-c611c741ed48 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-pp9m-qf39-hxjc is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-pp9m-qf39-hxjc is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-pp9m-qf39-hxjc. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-pp9m-qf39-hxjc in your dependencies?
O3 detects GHSA-pp9m-qf39-hxjc across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.