Description
In Eclipse Vert.x versions [4.0.0, 4.5.34] or [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the vertx-mail-client does not sanitize CR (\r) or LF (\n) characters in user-supplied email header names and values before writing them into the SMTP DATA section. A CR/LF sequence embedded in a name or value passed to MailMessage.addHeader(), MailMessage.setHeaders(), MailAttachment.addHeader(), or MailAttachment.setHeaders() is written verbatim to the wire, allowing an attacker to inject arbitrary headers (e.g. Bcc, Reply-To, Content-Type) or prepend body content to the outgoing message.



The same weakness affects MIME part metadata set via MailAttachment.setContentType(), setDisposition(), setDescription(), and setContentId(), which are written directly into MIME part headers without validation.



A secondary weakness in Utils.mustEncode(char) additionally allows a bare LF in a From display-name to bypass Q-encoding and reach the wire unchanged.



An unauthenticated attacker who can control any header name, header value, or attachment metadata field passed to the mail client (for example via a web form or API that feeds into MailMessage) can exploit this to redirect email copies, spoof headers, or tamper with message structure.



The impacted component is io.vertx:vertx-mail-client.
Published: 2026-10-14
Score: 6.9 Medium
EPSS: n/a
KEV: No
AI Analysis

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Remediation

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History

Wed, 14 Oct 2026 21:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 14 Oct 2026 20:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-93

Wed, 14 Oct 2026 19:00:00 +0000

Type Values Removed Values Added
Description In Eclipse Vert.x versions [4.0.0, 4.5.34] or [5.0.0,5.0.12] or [5.1.0,5.1.9] or [5.2.0, 5.2.0], the vertx-mail-client does not sanitize CR (\r) or LF (\n) characters in user-supplied email header names and values before writing them into the SMTP DATA section. A CR/LF sequence embedded in a name or value passed to MailMessage.addHeader(), MailMessage.setHeaders(), MailAttachment.addHeader(), or MailAttachment.setHeaders() is written verbatim to the wire, allowing an attacker to inject arbitrary headers (e.g. Bcc, Reply-To, Content-Type) or prepend body content to the outgoing message. The same weakness affects MIME part metadata set via MailAttachment.setContentType(), setDisposition(), setDescription(), and setContentId(), which are written directly into MIME part headers without validation. A secondary weakness in Utils.mustEncode(char) additionally allows a bare LF in a From display-name to bypass Q-encoding and reach the wire unchanged. An unauthenticated attacker who can control any header name, header value, or attachment metadata field passed to the mail client (for example via a web form or API that feeds into MailMessage) can exploit this to redirect email copies, spoof headers, or tamper with message structure. The impacted component is io.vertx:vertx-mail-client.
Title CRLF header injection in vertx-mail-client allows manipulation of outgoing SMTP messages
References
Metrics cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N'}


Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: eclipse

Published:

Updated: 2026-10-14T19:49:35.803Z

Reserved: 2026-09-29T08:34:19.768Z

Link: CVE-2026-102471

cve-icon Vulnrichment

Updated: 2026-10-14T19:48:45.989Z

cve-icon NVD

Status : Received

Published: 2026-10-14T19:17:05.180

Modified: 2026-10-14T20:17:28.363

Link: CVE-2026-102471

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses
  • CWE-93

    Improper Neutralization of CRLF Sequences ('CRLF Injection')