CVE-2021-27910

CVE-2021-27910 is a high-severity vulnerability in Acquia Mautic with a CVSS 3.x base score of 8.2. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Description

Insufficient sanitization / filtering allows for arbitrary JavaScript Injection in Mautic using the bounce management callback function. The values submitted in the "error" and "error_related_to" parameters of the POST request of the bounce management callback will be permanently stored and executed once the details page of an affected lead is opened by a Mautic user. An attacker with access to the bounce management callback function (identified with the Mailjet webhook, but it is assumed this will work uniformly across all kinds of webhooks) can inject arbitrary JavaScript Code into the "error" and "error_related_to" parameters of the POST request (POST /mailer/<product / webhook>/callback). It is noted that there is no authentication needed to access this function. The JavaScript Code is stored permanently in the web application and executed every time an authenticated user views the details page of a single contact / lead in Mautic. This means, arbitrary code can be executed to, e.g., steal or tamper with information.

Frequently asked questions

What is CVE-2021-27910?
Insufficient sanitization / filtering allows for arbitrary JavaScript Injection in Mautic using the bounce management callback function. The values submitted in the "error" and "error_related_to" parameters of the POST request of the bounce management callback will be permanently stored and executed once the details page of an affected lead is opened by a Mautic user. An attacker with access to the bounce management callback function (identified with the Mailjet webhook, but it is assumed this will work uniformly across all kinds of webhooks) can inject arbitrary JavaScript Code into the "error" and "error_related_to" parameters of the POST request (POST /mailer/<product / webhook>/callback). It is noted that there is no authentication needed to access this function. The JavaScript Code is stored permanently in the web application and executed every time an authenticated user views the details page of a single contact / lead in Mautic. This means, arbitrary code can be executed to, e.g., steal or tamper with information.
How severe is CVE-2021-27910?
CVE-2021-27910 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity high, and availability none.
Is CVE-2021-27910 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27910?
CVE-2021-27910 primarily affects Acquia Mautic. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-27910?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-27910 published?
CVE-2021-27910 was published on 2021-08-30 and last updated on 2026-06-17.

References

Affected products (4)

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