CVE-2021-27370Public exploitNetwork attack vector

Stored script execution via unescaped Last Name

Published Feb 22, 2021 · Updated Aug 3, 2024

Stored XSS in Monica 2.19.1 allows remote authenticated users to execute script in another user's browser via a crafted Last Name. The Contact form stores the Last Name value without neutralizing markup, and contact and audit-log views render it as unescaped HTML. An authenticated user must save the payload and another authenticated user must view the affected contact or audit log, exposing that viewer's in-session data and actions.

CVSS severity5.4
Medium
EPSS probability3.27%
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 Monica 2.19.1 allows remote authenticated users to execute script in another user's browser via a crafted Last Name. The Contact form stores the Last Name value without neutralizing markup, and contact and audit-log views render it as unescaped HTML. An authenticated user must save the payload and another authenticated user must view the affected contact or audit log, exposing that viewer's in-session data and actions.

The record

CVE
CVE-2021-27370
Published
Feb 22, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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

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 exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

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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