Eclipse Vert.x up to 4.5.34/5.0.12/5.1.9/5.2.0 vertx-mail-client crlf injection

Summaryinfo

A vulnerability was found in Eclipse Vert.x up to 4.5.34/5.0.12/5.1.9/5.2.0. It has been classified as critical. The affected element is the function MailMessage.addHeader/MailMessage.setHeaders/MailAttachment.addHeader/MailAttachment.setHeaders/MailAttachment.setContentType/setDisposition/describeContent/setContentId of the component vertx-mail-client. Performing a manipulation results in crlf injection. This vulnerability is reported as CVE-2026-102471. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability classified as critical has been found in Eclipse Vert.x up to 4.5.34/5.0.12/5.1.9/5.2.0. This affects the function MailMessage.addHeader/MailMessage.setHeaders/MailAttachment.addHeader/MailAttachment.setHeaders/MailAttachment.setContentType/setDisposition/describeContent/setContentId of the component vertx-mail-client. The manipulation with an unknown input leads to a crlf injection vulnerability. CWE is classifying the issue as 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. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-102471 since 09/29/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 10/14/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• Eclipse

Name

• Vert.x

Version

• 4.5.0
• 4.5.1
• 4.5.2
• 4.5.3
• 4.5.4
• 4.5.5
• 4.5.6
• 4.5.7
• 4.5.8
• 4.5.9
• 4.5.10
• 4.5.11
• 4.5.12
• 4.5.13
• 4.5.14
• 4.5.15
• 4.5.16
• 4.5.17
• 4.5.18
• 4.5.19
• 4.5.20
• 4.5.21
• 4.5.22
• 4.5.23
• 4.5.24
• 4.5.25
• 4.5.26
• 4.5.27
• 4.5.28
• 4.5.29
• 4.5.30
• 4.5.31
• 4.5.32
• 4.5.33
• 4.5.34
• 5.0
• 5.0.0
• 5.0.1
• 5.0.2
• 5.0.3
• 5.0.4
• 5.0.5
• 5.0.6
• 5.0.7
• 5.0.8
• 5.0.9
• 5.0.10
• 5.0.11
• 5.0.12
• 5.1
• 5.1.0
• 5.1.1
• 5.1.2
• 5.1.3
• 5.1.4
• 5.1.5
• 5.1.6
• 5.1.7
• 5.1.8
• 5.1.9
• 5.2.0

License

• open-source

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CPE 2.2info

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Entryinfo

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