misskey-dev/misskey

Misskey is an open source, federated social media platform. All Misskey servers running versions 10.93.0 and later, but prior to 2026.3.1, contain a vulnerability that allows importing other users' data due to lack of ownership validation. The impact of this vulnerability is estimated to be relatively low, as bad actors would require the ID corresponding to the target file for import. This vulnerability is fixed in 2026.3.1.

Misskey is an open source, federated social media platform. All Misskey servers prior to 2026.3.1 contain a vulnerability that allows bypassing HTTP signature verification. Although this is a vulnerability related to federation, it affects all servers regardless of whether federation is enabled or disabled. This vulnerability is fixed in 2026.3.1.

Misskey is an open source, federated social media platform. All Misskey servers running versions 8.45.0 and later, but prior to 2026.3.1, contain a vulnerability that allows bad actors access to data that they ordinarily wouldn't be able to access due to insufficient permission checks and proper input validation. This vulnerability occurs regardless of whether federation is enabled or not. This vulnerability could lead to a significant data breach. This vulnerability is fixed in 2026.3.1.

Misskey is an open source, federated social media platform. Starting in version 13.0.0-beta.16 and prior to version 2025.12.0, an actor who does not have permission to view favorites or clips can can export the posts and view the contents. Version 2025.12.0 fixes the issue.

Misskey is an open source, federated social media platform. Attackers who use an untrusted reverse proxy or not using a reverse proxy at all can bypass IP rate limiting by adding a forged X-Forwarded-For header. Starting with version 2025.9.1, an option (`trustProxy`) has been added in config file to prevent this from happening. However, it is initialized with an insecure default value before version 2025.12.0-alpha.2, making it still vulnerable if the configuration is not set correctly. This is patched in v2025.12.0-alpha.2 by flipping default value of `trustProxy` to `false`. Users of a trusted reverse proxy who are unsure if they manually overode this value should check their config for optimal behavior. Users are running Misskey with a trusted reverse proxy should not be affected by this vulnerability. From v2025.9.1 to v2025.11.1, workaround is available. Set `trustProxy: false` in config file.

Misskey is an open source, federated social media platform. Starting in version 12.31.0 and prior to version 2025.4.1, missing validation in `Mk:api` allows malicious AiScript code to access additional endpoints that it isn't designed to have access to. The missing validation allows malicious AiScript code to prefix a URL with `../` to step out of the `/api` directory, thereby being able to make requests to other endpoints, such as `/files`, `/url`, and `/proxy`. Version 2025.4.1 fixes the issue.

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.

Altair is a fork of Misskey v12. Affected versions lack of request validation and lack of authentication in the image proxy for compressing and resizing remote files could allow attacks that could affect availability, such as by abnormally increasing the CPU usage of the server on which this software is running or placing a heavy load on the network it is using. This issue has been fixed in v12.24Q4.1. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Misskey is an open source, federated social media platform. Some APIs using `HttpRequestService` do not properly check the target host. This vulnerability allows an attacker to send POST or GET requests to the internal server, which may result in a SSRF attack.It allows an attacker to send POST or GET requests (with some controllable URL parameters) to private IPs, enabling further attacks on internal servers. This issue has been addressed in version 2024.11.0-alpha.3. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Misskey is an open source, federated social media platform.In affected versions missing validation in `NoteCreateService.insertNote`, `ApPersonService.createPerson`, and `ApPersonService.updatePerson` allows an attacker to control the target of any "origin" links (such as the "view on remote instance" banner). Any HTTPS URL can be set, even if it belongs to a different domain than the note / user. Vulnerable Misskey instances will use the unverified URL for several clickable links, allowing an attacker to conduct phishing or other attacks against remote users. This issue has been addressed in version 2024.11.0-alpha.3. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Misskey is an open source, federated social media platform. In affected versions missing validation in `ApInboxService.update` allows an attacker to modify the result of polls belonging to another user. No authentication is required, except for a valid signature from any actor on any remote instance. Vulnerable Misskey instances will accept spoofed updates for remote polls. Local polls are unaffected. This issue has been addressed in version 2024.11.0-alpha.3. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Misskey is an open source, federated social media platform. In affected versions missing validation in `ApRequestService.signedGet` and `HttpRequestService.getActivityJson` allows an attacker to create fake user profiles and forged notes. The spoofed users will appear to be from a different instance than the one where they actually exist, and the forged notes will appear to be posted by a different user. Vulnerable Misskey instances will accept the spoofed objects as valid, allowing an attacker to impersonate other users and instances. The attacker retains full control of the spoofed user / note and can interact like a real account. This issue has been addressed in version 2024.11.0-alpha.3. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Misskey is an open source, federated social media platform. In affected versions missing validation in `ApRequestService.signedGet` allows an attacker to create fake user profiles that appear to be from a different instance than the one where they actually exist. These profiles can be used to impersonate existing users from the target instance. Vulnerable Misskey instances will accept spoofed users as valid, allowing an attacker to impersonate users on another instance. Attackers have full control of the spoofed user and can post, renote, or otherwise interact like a real account. This issue has been addressed in version 2024.11.0-alpha.3. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Misskey is an open source, federated social media platform. In affected versions FileServerService (media proxy) in github.com/misskey-dev/misskey 2024.10.1 or earlier did not detect proxy loops, which allows remote actors to execute a self-propagating reflected/amplified distributed denial-of-service via a maliciously crafted note. FileServerService.prototype.proxyHandler did not check incoming requests are not coming from another proxy server. An attacker can execute an amplified denial-of-service by sending a nested proxy request to the server and end the request with a malicious redirect back to another nested proxy request. Leading to unbounded recursion until the original request is timed out. This issue has been addressed in version 2024.11.0-alpha.3. Users are advised to upgrade. Users unable to upgrade may configure the reverse proxy to block requests to the proxy with an empty User-Agent header or one containing Misskey/. An attacker can not effectively modify the User-Agent header without making another request to the server.

Misskey is an open source, decentralized microblogging platform. Misskey doesn't perform proper normalization on the JSON structures of incoming signed ActivityPub activity objects before processing them, allowing threat actors to spoof the contents of signed activities and impersonate the authors of the original activities. This vulnerability is fixed in 2024.5.0.

Misskey is an open source, decentralized social media platform with ActivityPub support. Prior to version 2024.2.0, when fetching remote Activity Streams objects, Misskey doesn't check that the response from the remote server has a `Content-Type` header value of the Activity Streams media type, which allows a threat actor to upload a crafted Activity Streams document to a remote server and make a Misskey instance fetch it, if the remote server accepts arbitrary user uploads. The vulnerability allows a threat actor to impersonate and take over an account on a remote server that satisfies all of the following properties: allows the threat actor to register an account; accepts arbitrary user-uploaded documents and places them on the same domain as legitimate Activity Streams actors; and serves user-uploaded document in response to requests with an `Accept` header value of the Activity Streams media type. Version 2024.2.0 contains a patch for the issue.

Misskey is an open source, decentralized social media platform. Third-party applications may be able to access some endpoints or Websocket APIs that are incorrectly specified as [kind](https://github.com/misskey-dev/misskey/blob/406b4bdbe79b5b0b68fcdcb3c4b6e419460a0258/packages/backend/src/server/api/endpoints.ts#L811) or [secure](https://github.com/misskey-dev/misskey/blob/406b4bdbe79b5b0b68fcdcb3c4b6e419460a0258/packages/backend/src/server/api/endpoints.ts#L805) without the user's permission and perform operations such as reading or adding non-public content. As a result, if the user who authenticated the application is an administrator, confidential information such as object storage secret keys and SMTP server passwords will be leaked, and general users can also create invitation codes without permission and leak non-public user information. This is patched in version [2023.12.1](https://github.com/misskey-dev/misskey/commit/c96bc36fedc804dc840ea791a9355d7df0748e64).

Nexkey is a lightweight fork of Misskey v12 optimized for small to medium size servers. Prior to 12.23Q4.5, Nexkey allows external apps using tokens issued by administrators and moderators to call admin APIs. This allows malicious third-party apps to perform operations such as updating server settings, as well as compromise object storage and email server credentials. This issue has been patched in 12.23Q4.5.

Misskey is an open source, decentralized social media platform. Misskey's missing signature validation allows arbitrary users to impersonate any remote user. This issue has been patched in version 2023.11.1-beta.1.

Nexkey is a fork of Misskey, an open source, decentralized social media platform. Prior to version 12.121.9, incomplete URL validation can allow users to bypass authentication for access to the job queue dashboard. Version 12.121.9 contains a fix for this issue. As a workaround, it may be possible to avoid this by blocking access using tools such as Cloudflare's WAF.

Misskey is an open source, decentralized social media platform. Prior to version 2023.9.0, by editing the URL, a user can bypass the authentication of the Bull dashboard, which is the job queue management UI, and access it. Version 2023.9.0 contains a fix. There are no known workarounds.

Misskey is an open source, decentralized social media platform. In versions prior to 13.3.3 SQL injection is possible due to insufficient parameter validation in the note search API by tag (notes/search-by-tag). This has been fixed in version 13.3.3. Users are advised to upgrade. Users unable to upgrade should block access to the `api/notes/search-by-tag` endpoint.

Misskey is an open source, decentralized social media platform. In versions prior to 13.3.2 the URL preview function is subject to a cross site scripting vulnerability due to insufficient URL validation. Arbitrary JavaScript is executed when a malicious URL is loaded in the `View in Player` or `View in Window` preview. This has been fixed in version 13.3.2. Users are advised to upgrade. Users unable to upgrade should avoid usage of the `View in Player` or `View in Window` functions.

Misskey is an open source, decentralized social media platform. Due to insufficient validation of the redirect URL during `miauth` authentication in Misskey, arbitrary JavaScript can be executed when a user allows the link. All versions below 13.3.1 (including 12.x) are affected. This has been fixed in version 13.3.1. Users are advised to upgrade. Users unable to upgrade should not allow authentication of untrusted apps.

Misskey is an open source, decentralized social media platform. In versions prior to 13.5.0 the link to the instance to the sender that appears when viewing a user or note received through ActivityPub is not properly validated, so by inserting a URL with a javascript scheme an attacker may execute JavaScript code in the context of the recipient. This issue has been fixed in version 13.5.0. Users are advised to upgrade. Users unable to upgrade should not "view on remote" for untrusted instances.

Misskey is an open source, decentralized microblogging platform. In affected versions a Server-Side Request Forgery vulnerability exists in "Upload from URL" and remote attachment handling. This could result in the disclosure of non-public information within the internal network. This has been fixed in 12.90.0. However, if you are using a proxy, you will need to take additional measures. As a workaround this exploit may be avoided by appropriately restricting access to private networks from the host where the application is running.

Misskey is a decentralized microblogging platform. In versions of Misskey prior to 12.51.0, malicious actors can use the web client built-in dialog to display a malicious string, leading to cross-site scripting (XSS). XSS could compromise the API request token. This issue has been fixed in version 12.51.0. There are no known workarounds aside from upgrading.