CVE-2023-28837: Wagtail vulnerable to denial-of-service via memory exhaustion when uploading large files
Impact
A memory exhaustion bug exists in Wagtail's handling of uploaded images and documents. For both images and documents, files are loaded into memory during upload for additional processing. A user with access to upload images or documents through the Wagtail admin interface could upload a file so large that it results in a crash or denial of service.
The vulnerability is not exploitable by an ordinary site visitor without access to the Wagtail admin. It can only be exploited by admin users with permission to upload images or documents.
Image uploads are restricted to 10MB by default, however this validation only happens on the frontend and on the backend after the vulnerable code.
Patches
Patched versions have been released as Wagtail 4.1.4 (for the LTS 4.1 branch) and Wagtail 4.2.2 (for the current 4.2 branch).
Workarounds
Site owners who are unable to upgrade to the new versions are encouraged to add extra protections outside of Wagtail to limit the size of uploaded files. Exactly how this is done will vary based on your hosting environment, but here are a few references for common setups:
- Nginx: clientmaxbodysize - Apache: LimitRequestBody - Cloudflare: Already imposes a limit of 100MB - 500MB depending on plan - CloudFront: SizeConstraint - Traefik: traefik.http.middlewares.limit.buffering.maxRequestBodyBytes
The changes themselves are deep inside Wagtail, making patching incredibly difficult.
Other sources
Wagtail is an open source content management system built on Django. Prior to versions 4.1.4 and 4.2.2, a memory exhaustion bug exists in Wagtail's handling of uploaded images and documents. For both images and documents, files are loaded into memory during upload for additional processing. A user with access to upload images or documents through the Wagtail admin interface could upload a file so large that it results in a crash of denial of service.
The vulnerability is not exploitable by an ordinary site visitor without access to the Wagtail admin. It can only be exploited by admin users with permission to upload images or documents.
Image uploads are restricted to 10MB by default, however this validation only happens on the frontend and on the backend after the vulnerable code.
Patched versions have been released as Wagtail 4.1.4 and Wagtail 4.2.2). Site owners who are unable to upgrade to the new versions are encouraged to add extra protections outside of Wagtail to limit the size of uploaded files.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is CVE-2023-28837?
CVE-2023-28837 is a memory exhaustion vulnerability in Wagtail, an open source content management system built on Django.
How does CVE-2023-28837 affect Wagtail?
CVE-2023-28837 affects Wagtail versions 4.1.4 and 4.2.2, causing a memory exhaustion issue during the handling of uploaded images and documents.
What is the severity of CVE-2023-28837?
CVE-2023-28837 has a severity value of 4.9, which is considered medium.
How can I check if my version of Wagtail is affected by CVE-2023-28837?
You can check if your version of Wagtail is affected by CVE-2023-28837 by verifying if it is version 4.1.4 or 4.2.2.
How do I fix CVE-2023-28837?
To fix CVE-2023-28837, update your Wagtail installation to version 4.1.5 or 4.2.3 or later.