CVE-2026-34975CWE-93

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

High · published April 6, 2026

CVSS v3.1
8.5
EPSS
0%
Percentile
22.7
In the wild
Unconfirmed
What it 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.

The record
Technical detail
CVSS v3.1
8.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00311 · 22.7th percentile
Weakness
CWE-93 · Improper Neutralization of CRLF Sequences ('CRLF Injection')
Published
2026-04-06T16:10Z
EPSS history
Timeline
  • 06 APR 16:10Z
    Plunk has a CRLF Email Header Injection in raw MIME message construction allows authenticated API user to inject arbitrary email headers
    cvelistv5