CVE-2021-27910Network attack vector

Stored XSS via unsanitized bounce callback errors

Published Aug 30, 2021 · Updated Sep 17, 2024

Stored XSS in Mautic before 3.3.4 and before 4.0.0 allows remote attackers to run JavaScript when a user opens a contact. The unauthenticated bounce-management callback stores the error and error_related_to POST fields without sufficient sanitization and renders them in a lead details page. Execution requires an authenticated user to open the affected contact, after which the payload runs in that user's browser and can read or alter information available to the session.

CVSS severity8.2
High
EPSS probability0.70%
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 Mautic before 3.3.4 and before 4.0.0 allows remote attackers to run JavaScript when a user opens a contact. The unauthenticated bounce-management callback stores the error and error_related_to POST fields without sufficient sanitization and renders them in a lead details page. Execution requires an authenticated user to open the affected contact, after which the payload runs in that user's browser and can read or alter information available to the session.

The record

CVE
CVE-2021-27910
Published
Aug 30, 2021
Updated
Sep 17, 2024
Vendor
Acquia
Product
Mautic
Classifications
CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 30, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 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=unspecified <3.3.4
  2. Affected versionversion=unspecified <4.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Acquia · Mauticversion=unspecified <3.3.4; version=unspecified <4.0.0

Published CVSS scores

8.2MauticCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/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
Privilegesunauthenticated
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.

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Technologies

Your stack

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Your stack

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