CVE-2021-43856Network attack vector

Stored XSS via inline non-image file rendering

Published Dec 27, 2021 · Updated Aug 4, 2024

Stored XSS in Wiki.js 2.5.263 and earlier allows remote authenticated users to execute JavaScript via uploaded non-image files. Asset.getAsset returned unsafe non-image files without an attachment Content-Disposition header, allowing browsers to render their active content inline. Exploitation requires upload access and a victim who opens the stored file directly; ordinary Wiki.js page views do not trigger it.

CVSS severity8.2
High
EPSS probability0.89%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in Wiki.js 2.5.263 and earlier allows remote authenticated users to execute JavaScript via uploaded non-image files. Asset.getAsset returned unsafe non-image files without an attachment Content-Disposition header, allowing browsers to render their active content inline. Exploitation requires upload access and a victim who opens the stored file directly; ordinary Wiki.js page views do not trigger it.

The record

CVE
CVE-2021-43856
Published
Dec 27, 2021
Updated
Aug 4, 2024
Vendor
Requarks.io
Product
Wiki.js
Classifications
CWE-79, T1203
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 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=< 2.5.264

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Requarks.io · Wiki.jsversion=< 2.5.264

Published CVSS scores

5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/A:N
8.2GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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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