CVE-2021-39169

Name: CVE-2021-39169
Creator: NVD / NIST
Published: 2021-08-27T13:15:07.02+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.4/10EPSS 0.74%

Last modified Jun 17, 2026

CVE-2021-39169 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. 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). EPSS estimates a 0.74% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

5.4/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

0.74%

49.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Misskey	Misskey	< 12.51.0

References

https://github.com/misskey-dev/misskey/commit/ec203f7f795766f76b55fecc9248168c1cdf6c99Patch, Third Party Advisory
https://github.com/misskey-dev/misskey/security/advisories/GHSA-pmmv-jwqh-f5wwPatch, Third Party Advisory
https://github.com/misskey-dev/misskey/commit/ec203f7f795766f76b55fecc9248168c1cdf6c99Patch, Third Party Advisory
https://github.com/misskey-dev/misskey/security/advisories/GHSA-pmmv-jwqh-f5wwPatch, Third Party Advisory

Timeline

Published: Aug 27, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-39169?

How severe is CVE-2021-39169?

CVE-2021-39169 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 0.74% probability of exploitation in the next 30 days.

How do I fix CVE-2021-39169?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-39169?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST