Vulnerability Description
Misskey is an open source, federated social media platform. Starting in version 12.0.0 and prior to version 2025.4.1, due to an oversight in the validation performed in `UrlPreviewService` and `MkUrlPreview`, it is possible for an attacker to inject arbitrary CSS into the `MkUrlPreview` component. `UrlPreviewService.wrap` falls back to returning the original URL if it's using a protocol that is likely to not be understood by Misskey, IE something other than `http` or `https`. This both can de-anonymize users and_allow further attacks in the client. Additionally, `MkUrlPreview` doesn't escape CSS when applying a `background-image` property, allowing an attacker to craft a URL that applies arbitrary styles to the preview element. Theoretically, an attacker can craft a CSS injection payload to create a fake error message that can deceive the user into giving away their credentials or similar sensitive information. Version 2025.4.1 contains a patch for the issue.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Misskey | Misskey | >= 12.0.0, < 2025.4.1 |
Related Weaknesses (CWE)
References
- https://github.com/misskey-dev/misskey/commit/d10fdfe9738b17a9d81037c031b40a2cc4Patch
- https://github.com/misskey-dev/misskey/security/advisories/GHSA-3p2w-xmv5-jm95Vendor Advisory
FAQ
What is CVE-2025-46340?
CVE-2025-46340 is a vulnerability with a CVSS score of 7.2 (HIGH). Misskey is an open source, federated social media platform. Starting in version 12.0.0 and prior to version 2025.4.1, due to an oversight in the validation performed in `UrlPreviewService` and `MkUrlP...
How severe is CVE-2025-46340?
CVE-2025-46340 has been rated HIGH with a CVSS base score of 7.2/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2025-46340?
Check the references section above for vendor advisories and patch information. Affected products include: Misskey Misskey.