CVE-2026-91831
Received Received - Intake

Email Header Injection in Subscribe to Comments WordPress Plugin

Publication date: 2026-10-19

Last updated on: 2026-10-19

Assigner: WPScan

Description
The Subscribe to Comments WordPress plugin before 2.3.3 does not sanitise newline characters from a notification sender-name setting before using it in e-mail headers, allowing users with Author-level access and above to inject arbitrary e-mail headers, such as a hidden Bcc, and to spoof the sender.

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Meta Information

Published
2026-10-19
Last Modified
2026-10-19
Generated
2026-10-19
AI Q&A
2026-10-19
EPSS Evaluated
N/A
NVD
CVE-2026-91831
EUVD
EUVD-2026-104101

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
Unknown Subscribe to Comments 2.3

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-93 The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.

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Executive Summary

This vulnerability exists in the Subscribe to Comments WordPress plugin before version 2.3.3. It allows users with Author-level access or higher to inject arbitrary email headers, such as Bcc, and spoof the sender by not sanitizing newline characters in the notification sender-name setting before using it in email headers.

Detection Guidance

Check the installed version of the Subscribe to Comments plugin. If it is between 2.3 and 2.3.2, the system is vulnerable. Use WordPress admin panel or run: wp plugin list | grep subscribe-to-comments in WP-CLI.

Impact Analysis

An attacker with Author-level access could send emails that appear to come from a trusted source, potentially tricking recipients into disclosing sensitive information or installing malware. They could also secretly send copies of emails to unauthorized recipients via Bcc.

Compliance Impact

This vulnerability could lead to unauthorized data exposure, violating GDPR's data protection principles or HIPAA's confidentiality requirements. It may result in data breaches, unauthorized disclosures, and non-compliance with privacy regulations.

Mitigation Strategies

Update the Subscribe to Comments plugin to version 2.3.3 or later immediately. If updating is not possible, restrict Author-level and higher user access to prevent exploitation until the update is applied.

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