CVE-2021-39169Network attack vector

API token theft via unsanitized dialog HTML

Published Aug 27, 2021 · Updated Aug 4, 2024

Cross-site scripting in the Misskey web client before 12.51.0 allows remote authenticated users to steal API request tokens via a dialog. The title and text bindings in src/client/components/dialog.vue pass attacker-influenced strings to Vue v-html without sanitizing the resulting HTML. A user must display the malicious dialog content, after which script runs in the web-client context and can compromise that user's API token.

CVSS severity8.0
High
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in the Misskey web client before 12.51.0 allows remote authenticated users to steal API request tokens via a dialog. The title and text bindings in src/client/components/dialog.vue pass attacker-influenced strings to Vue v-html without sanitizing the resulting HTML. A user must display the malicious dialog content, after which script runs in the web-client context and can compromise that user's API token.

The record

CVE
CVE-2021-39169
Published
Aug 27, 2021
Updated
Aug 4, 2024
Vendor
Misskey Project
Product
Misskey
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 12.51.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Misskey Project · Misskeyversion=< 12.51.0

Published CVSS scores

8.0GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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