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Path Traversal in django-s3file

Critical severity GitHub Reviewed Published Jun 6, 2022 in codingjoe/django-s3file • Updated Sep 16, 2024

Package

pip django-s3file (pip)

Affected versions

< 5.5.1

Patched versions

5.5.1

Description

Impact

It was possible to traverse the entire AWS S3 bucket and in most cases to access or delete files.
The issue was discovered by the maintainer. There were no reports of the vulnerability
being known to or exploited by a third party, before the release of the patch.

If the AWS_LOCATION setting was set, traversal was limited to that location only.
If all your files handling views (like form views) require authentication or special permission, the thread is limited to privileged users.

Patches

The vulnerability has been fixed in version 5.5.1 and above.

Workarounds

There is no feasible workaround. We must urge all users to immediately updated to a patched version.

Detailed attack vector description

An attacker may use a request with malicious form data to traverse the entire AWS S3 bucket and perform destructive operations.

An attack could look as follows:

curl -X POST -F "s3file=file" -F "file=/priviliged/location/secrets.txt" https://www.example.com/any/path/will/work/

This will result in a request with files set and opened:

>>> request.FILES.getlist("file")
[File("/priviliged/location/secrets.txt")]

Since this behavior is injected via a middleware, any view can be called this way and will carry any files defined by the attacker.

Via the s3file form field, any input name can be specified, including multiple inputs. For each input, multiple files can be freely
picked of the S3 bucket.

Scenarios and their practicality

There are four scenarios that would be considered practical in most setups:

  1. Illegal file injection,
  2. file deletion,
  3. file retrieval & tree traversal.
  4. code injection & remote code execution.
File deletion

An attacker knows the location of a privileged file, like a static asset. Next, the file is injected into a form view. The upload to function will move the file to a new location. This is effectively deleting the file, since the previous references to it are invalid, and will cause S3 to return a 404. Furthermore, the new location is unknown to the site operator.

File retrieval & tree traversal

An attacker knows the URL of a secret file and injects it into a form view. The view will move the file to a public location, making it accessible to the attacker. Since most form views will not be rate limited, this could also be used to guess files and traverse the file tree.

Illegal file injection

An attacker uses any form to upload a file to the temporary upload location. Next, the attacker injects that file into a request, does not validate the contents or is not equipped to handle the mime type. The latter could be used as a potential DOS vector.

In practice, this is not a practical risk in most hardened setup. Files should always be sanitized before processing, since files can be included in a request even without this security issues.

For more information

If you have any questions or comments about this advisory:

References

@codingjoe codingjoe published to codingjoe/django-s3file Jun 6, 2022
Published to the GitHub Advisory Database Jun 6, 2022
Reviewed Jun 6, 2022
Published by the National Vulnerability Database Jun 9, 2022
Last updated Sep 16, 2024

Severity

Critical

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 High
Integrity High
Availability None
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:H/VI:H/VA:N/SC:N/SI:N/SA:N

EPSS score

0.286%
(69th percentile)

CVE ID

CVE-2022-24840

GHSA ID

GHSA-4w8f-hjm9-xwgf

Credits

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