What’s Vulnerable › Vulnerabilities

CVE-2021-39195: Server-Side Request Forgery vulnerability in misskey

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-09-07 · updated 2026-06-17
• Weakness: CWE-918

Description

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.

Affected products

• misskey-dev misskey: before 12.90.0 — fixed in 12.90.0

How to fix

Upgrade to a fixed version: misskey-dev misskey 12.90.0. Check the vendor advisory for mitigations.

References

• https://github.com/misskey-dev/misskey/blob/develop/CHANGELOG.md#12900-20210904
• https://github.com/misskey-dev/misskey/commit/e1a8b158e04ad567d92d8daf3cc0898ee18f1a2e
• https://github.com/misskey-dev/misskey/security/advisories/GHSA-mqv7-gxh4-r5vf
• https://github.com/misskey-dev/misskey/blob/develop/CHANGELOG.md#12900-20210904
• https://github.com/misskey-dev/misskey/commit/e1a8b158e04ad567d92d8daf3cc0898ee18f1a2e
• https://github.com/misskey-dev/misskey/security/advisories/GHSA-mqv7-gxh4-r5vf

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