CVE-2021-42136Public exploitNetwork attack vector

Administrator escalation via stored XSS

Published Apr 13, 2022 · Updated Aug 4, 2024

Stored cross-site scripting in REDCap before 11.4.0 allows remote authenticated users to execute JavaScript in an administrator's browser. The Missing Data Codes functionality stores attacker-supplied values without adequate output encoding, causing the payload to execute when the value is rendered. Exploitation requires a victim administrator to view the stored value; the script can forge requests that change account privileges and other data.

CVSS severity9.0
Critical
EPSS probability4.66%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored cross-site scripting in REDCap before 11.4.0 allows remote authenticated users to execute JavaScript in an administrator's browser. The Missing Data Codes functionality stores attacker-supplied values without adequate output encoding, causing the payload to execute when the value is rendered. Exploitation requires a victim administrator to view the stored value; the script can forge requests that change account privileges and other data.

The record

CVE
CVE-2021-42136
Published
Apr 13, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 13, 2022CVE 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.0NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
3.5NVDAV:N/AC:M/Au:S/C:N/I:P/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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

Public exploit references

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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