VULNERABILITY INTELLIGENCE

CVE-2025-46340

CVSS score7.2 HIGH
EPSS probability0.25%
CISA KEVNot currently listed
Published2025-05-05
Last modified2026-06-17
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

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.

Weakness classification

  • security-advisories@github.com: CWE-20

Primary references