CVE-2021-43855Network attack vector

Stored XSS via MIME-spoofed SVG upload

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 through a crafted SVG upload. The upload path in server/models/assets.js checked only the client-supplied MIME type before sanitizing SVG content and ignored the .svg extension. Exploitation requires upload access, a spoofed non-SVG MIME type, and another user directly viewing the stored SVG; ordinary image embedding does not execute it.

CVSS severity5.4
Medium
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 through a crafted SVG upload. The upload path in server/models/assets.js checked only the client-supplied MIME type before sanitizing SVG content and ignored the .svg extension. Exploitation requires upload access, a spoofed non-SVG MIME type, and another user directly viewing the stored SVG; ordinary image embedding does not execute it.

The record

CVE
CVE-2021-43855
Published
Dec 27, 2021
Updated
Aug 4, 2024
Vendor
Requarks.io
Product
Wiki.js
Classifications
CWE-79, T1059.007, T1204.002
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

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')
T1059.007JavaScript/JScript
T1204.002Malicious File

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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