useplunk up to 0.7.x MIME Message crlf injection

Summaryinfo

A vulnerability marked as problematic has been reported in useplunk plunk up to 0.7.x. This affects an unknown part of the component MIME Message Handler. This manipulation causes crlf injection. This vulnerability is registered as CVE-2026-34975. Remote exploitation of the attack is possible. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical was found in useplunk plunk up to 0.7.x. Affected by this vulnerability is an unknown code of the component MIME Message Handler. The manipulation with an unknown input leads to a crlf injection vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

Plunk is an open-source email platform built on top of AWS SES. Prior to 0.8.0, a CRLF header injection vulnerability was discovered in SESService.ts, where user-supplied values for from.name, subject, custom header keys/values, and attachment filenames were interpolated directly into raw MIME messages without sanitization. An authenticated API user could inject arbitrary email headers (e.g. Bcc, Reply-To) by embedding carriage return/line feed characters in these fields, enabling silent email forwarding, reply redirection, or sender spoofing. The fix adds input validation at the schema level to reject any of these fields containing \r or \n characters, consistent with the existing validation already applied to the contentId field. This vulnerability is fixed in 0.8.0.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-34975 since 03/31/2026. The exploitation appears to be easy. The attack can be launched remotely. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 0.8.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CNNVD (CNNVD-202604-994). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• useplunk

Name

• plunk

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7

Website

• Product: https://github.com/useplunk/plunk/

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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