GHSA-277c-5vvj-9pwx CVE-2024-32871
Flooding Server with Thumbnail files
- Severity
- 7.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.76%
- Chance of exploitation in the next 30 days. Higher than 55.39% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-770 Allocation of Resources Without Limits or Throttling
- Fix
11.2.4- Upgrade pimcore/pimcore to this version or later
Description
Details
1. All Imagick supported Fileformats are served without filtering
The Thumbnail endpoint does not check against any filters what file formats should be served. We can transcode the image in all formats imagemagick supports. With that we can create Files that are much larger in filesize than the original. For example we can create a .txt file for all thumbnails, and we get the text representation of the image.
We can demonstrate that with the pimcore demo:
This Thumbnail is found on the Frontend: https://demo.pimcore.fun/Sample%20Content/Background%20Images/317/image-thumb__317__standardTeaser/11.8c64bd89.avif (12kb Filesize)
We can generate a text representation by simply changing the file extension: https://demo.pimcore.fun/Sample%20Content/Background%20Images/317/image-thumb__317__standardTeaser/11.8c64bd89.txt (4.59mb Filesize)
Other (large) fileformats we tested: ftxt, dip, bmp, bmp3, bmp2, farbfeld, cmyk, cmyka, ycbcr, ycbcra and many more (just check imagemagick supported formats)
With that we can fill the available space of a server really easy.
With formats like yaml or json we can also expose exif data of the original image file - could be a concern with gps data in user uploaded images.
TLDR
- we can generate all imagemagick supported formats with all thumbnail configs
- all configs were the format is set to "auto (Web-optimized)" are vulnerable
- private (exif) data can be exposed.
- We can flood the the server with a bunch of files that are a multiple magnitudes of the original thumbnail size (see txt example), for all thumbnail configs, with every image that we find (scriptable)
Proposed Solution
Implement a list of allowed formats that the developer can modify if needed, if a file is requested in another format than listed, pimcore should return either "/bundles/pimcoreadmin/img/filetype-not-supported.svg" or a 404.
pimcore:
thumbnails:
allowed_formats: ['jpg', 'png', 'avif', 'webp', 'gif']
For non-maintained Pimcore versions (<11), the webserver config could be used to only serve files that should be allowed.
2. Non Web optimized file formats (ORIGINAL, JPG, PNG) creates duplicated files on Server
With Thumbnail config that are configured to serve non web optimized file formats (such as ORIGINAL, jpg, png, print, etc) we can create files with arbitrary file formats that are saved to disk.
For example, the thumbnail configuration "print_backgroundimage" (in the pimcore demo) can be used to create files such as:
https://demo.pimcore.fun/Car%20Images/jaguar/3/image-thumb__3__print_backgroundimage/auto-3095119.aaa https://demo.pimcore.fun/Car%20Images/jaguar/3/image-thumb__3__print_backgroundimage/auto-3095119.aab https://demo.pimcore.fun/Car%20Images/jaguar/3/image-thumb__3__print_backgroundimage/auto-3095119.aac
Each request creates a new copy of the original (jpg) thumbnail file. The server can be flooded with a bunch of files.
Code for this mechanism is here: https://github.com/pimcore/pimcore/blob/11.x/models/Asset/Service.php#L621-L623
Proposed Solution
Use same filtered list from "All Imagick supported Fileformats are served without filtering" and do not copy the arbitrary file to disk, just serve the original image file under the "new" name.
3. Scaling Factor is not limited and can be modified via url
We can scale each thumbnail to an arbitrary factor with @<float>x added to the request url.
For example:
https://demo.pimcore.fun/Sample%20Content/Background%20Images/317/image-thumb__317__standardTeaser/11.8c64bd89@1x.avif https://demo.pimcore.fun/Sample%20Content/Background%20Images/317/image-thumb__317__standardTeaser/11.8c64bd89@1.01x.avif https://demo.pimcore.fun/Sample%20Content/Background%20Images/317/image-thumb__317__standardTeaser/11.8c64bd89@1.08x.avif https://demo.pimcore.fun/Sample%20Content/Background%20Images/317/image-thumb__317__standardTeaser/11.8c64bd89@2x.avif
If the thumbnail config allows "forced" resizing, we could also do something like:
Each request will create a new file, flooding the server with more files. If the factor is big enough, we can also max out the CPU with a single request for quite some time (only really a problem with "forced")
In combination with the first vulnerability we can also generate (large) text files for scaled images:
https://demo.pimcore.fun/Sample%20Content/Background%20Images/317/image-thumb__317__standardTeaser/11.8c64bd89@4x.txt (6.6 mb filesize)
Proposed solution
Limit scale factors with an allowlist:
pimcore:
thumbnails:
allowed_scale_factors: [1.25, 1.5, 2, 4]
Impact
All Pimcore Instances are affected, as far as we can see, also all versions
Affected versions
Packagist
| Package | Vulnerable | Fixed in |
|---|---|---|
| pimcore/pimcore | >= 11.0.0, < 11.2.4 |
11.2.4 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
pimcore/pimcore Packagist → 11.2.4
- composer
composer require pimcore/pimcore:^11.2.4
Severity breakdown
CVSS 3.1 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-770: Allocation of Resources Without Limits or Throttling
The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.
How to prevent it
- Requirements: Clearly specify the minimum and maximum expectations for capabilities, and dictate which behaviors are acceptable when resource allocation reaches limits.
- Architecture and Design: Limit the amount of resources that are accessible to unprivileged users. Set per-user limits for resources. Allow the system administrator to define these limits. Be careful to avoid CWE-410.
- Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place, and it will help the administrator to identify who is committing the abuse. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- Architecture and Design: For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
- Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, typically by using increasing time delays uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution can be difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply requires more resources on the part of the attacker.
- Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
- Architecture and Design, Implementation: If the program must fail, ensure that it fails gracefully (fails closed). There may be a temptation to simply let the program fail poorly in cases such as low memory conditions, but an attacker may be able to assert control before the software has fully exited. Alternately, an uncontrolled failure could cause cascading problems with other downstream components; for example, the program could send a signal to a downstream process so the process immediately knows that a problem has occurred and has a better chance of recovery. Ensure that all failures in resource allocation place the system into a safe posture.
- Operation, Architecture and Design: Use quotas or other resource-limiting settings provided by the operating system or environment. For example, when managing system resources in POSIX, setrlimit() can be used to set limits for certain types of resources, and getrlimit() can determine how many resources are available. However, these functions are not available on all operating systems. When the current levels get close to the maximum that is defined for the application (see CWE-770), then limit the allocation of further resources to privileged users; alternately, begin releasing resources for less-privileged users. While this mitigation may protect the system from attack, it will not necessarily stop attackers from adversely impacting other users. Ensure that the application performs the appropriate error checks and error handling in case resources become unavailable (CWE-703).
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-23rh-xw42-fq82 Pimcore: SQL Injection in Custom Reports via Malicious Report Configuration | High | Also affects pimcore/pimcore |
| GHSA-9x44-4gxf-8c25 Pimcore Vulnerable to Remote Code Execution via DataObject Class-Definition Field Name | Critical | Also affects pimcore/pimcore |
| GHSA-w23p-wrp7-ch38 Pimcore Hotspotimage getDataFromResource() unrestricted Serialize::unserialize over object-store column (PHP Object Injection, CWE-502) | Critical | Also affects pimcore/pimcore |
| GHSA-2mhj-fhvg-v428 Pimcore: ClassDefinition UID regex missing end anchor allows SQL injection via Block.php unquoted table name | High | Also affects pimcore/pimcore |
| GHSA-7p36-fq2r-4h7r Pimcore CMS Twig Sandbox Bypass via SecurityPolicy checkMethodAllowed | High | Also affects pimcore/pimcore |
| GHSA-jwcc-gv4m-93x6 Pimcore has a CustomReports Share Bypass | High | Also affects pimcore/pimcore |
| GHSA-332x-r494-54fq Pimcore has a WordExport Authorization Bypass for Unauthorized Document Export | Medium | Also affects pimcore/pimcore |
| GHSA-wc7j-g8wx-m2qx Pimcore: Missing Authorization in WebDAV MOVE via unchecked asset move handling | High | Also affects pimcore/pimcore |
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