CVE-2026-34975 HIGH

CVE-2026-34975: Plunk has a CRLF Email Header Injection in raw MIME message construction allows authenticated API user to inject arbitrary email headers

Vendor Useplunk
Product plunk
Weakness CWE-93 · CRLF injection
Published April 6, 2026
Last update April 7, 2026

CVSS base score

8.5/10
Attack vector Network
Attack complexity Low
Privileges required Low
User interaction None
Confidentiality High
Integrity Low

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

April 6, 2026 CVE published
April 7, 2026 Record updated