CVE-2021-39175Network attack vector

Arbitrary script execution via permissive slide CSP

Published Aug 30, 2021 · Updated Aug 4, 2024

Cross-site scripting in HedgeDoc before 1.9.0 allows remote attackers to execute arbitrary JavaScript through slide-mode speaker notes. The slide renderer accepts attacker-controlled iframes while the default Content Security Policy permits inline scripts and trusted JSONP sources that bypass script restrictions. Exploitation requires a user to open the crafted speaker view or a page embedding the instance, enabling script execution in that user's browser context.

CVSS severity8.1
High
EPSS probability0.60%
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 HedgeDoc before 1.9.0 allows remote attackers to execute arbitrary JavaScript through slide-mode speaker notes. The slide renderer accepts attacker-controlled iframes while the default Content Security Policy permits inline scripts and trusted JSONP sources that bypass script restrictions. Exploitation requires a user to open the crafted speaker view or a page embedding the instance, enabling script execution in that user's browser context.

The record

CVE
CVE-2021-39175
Published
Aug 30, 2021
Updated
Aug 4, 2024
Vendor
HedgeDoc
Product
HedgeDoc
Classifications
CWE-74, CWE-346, T1189
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 30, 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=< 1.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

HedgeDoc · HedgeDocversion=< 1.9.0

Published CVSS scores

8.1GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
CWE-346Origin Validation Error
T1189Drive-by Compromise

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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