CVE-2023-28837

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: client_max_body_size
• 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.

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.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2023-28837 has a CVSS score of 4.4 (Medium). The vector is network-reachable, high privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.2.2, 4.1.4); upgrading removes the vulnerable code path.

Kodem intelligence

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).

1. What is CVE-2023-28837? CVE-2023-28837 is a medium-severity uncontrolled resource consumption vulnerability in wagtail (pip), affecting versions >= 4.2, < 4.2.2. It is fixed in 4.2.2, 4.1.4. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2023-28837? CVE-2023-28837 has a CVSS score of 4.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of wagtail are affected by CVE-2023-28837? wagtail (pip) versions >= 4.2, < 4.2.2 is affected.
4. Is there a fix for CVE-2023-28837? Yes. CVE-2023-28837 is fixed in 4.2.2, 4.1.4. Upgrade to this version or later.
5. Is CVE-2023-28837 exploitable, and should I be worried? Whether CVE-2023-28837 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
6. What actually determines whether CVE-2023-28837 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.
7. How do I fix CVE-2023-28837?
   • Upgrade wagtail to 4.2.2 or later
   • Upgrade wagtail to 4.1.4 or later