What’s Vulnerable › Vulnerabilities
CVE-2026-34975: Plunk has a CRLF Email Header Injection in raw MIME message construction allows authenticated API user to inject arbitrary email headers
- Severity: medium (CVSS 4.3 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.2% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-04-06 · updated 2026-10-24
- Weakness: CWE-93
Description
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.
Affected products
- useplunk plunk: before 0.8.0 — fixed in 0.8.0
How to fix
Upgrade to a fixed version: useplunk plunk 0.8.0. Check the vendor advisory for mitigations.
References
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