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CVE-2026-34975

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

8.5 HighPublic exploit

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
Low
Availability
None

Exploit likelihood

0.20%Up 0.2 points since Apr 7, 2026
90%50%10%1%

What each source reports

CVE List Score used 8.5

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

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.

Record
CVE-2026-34975
CVSS 3.1
8.5 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
Weakness
CWE-93
Updated
2026-11-02
EUVDEUVD-2026-19359 8.5

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.

Record
EUVD-2026-19359
CVSS 3.1
8.5 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
Updated
2026-11-02
NVD 8.5

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.

Record
CVE-2026-34975
CVSS 3.1
8.5 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
CVSS 3.1
4.3 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
Weakness
CWE-93
Updated
2026-11-02
OSV 8.5

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

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.

Record
CVE-2026-34975
CVSS 3.1
8.5 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
Weakness
CWE-93
Updated
2026-11-02

Affected products

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
SourceLinkDate
PoC in GitHubromain-deperne/CVE-2026-349752026-04-29

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV, PoC in GitHub

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-34975 is a high vulnerability (CVSS 8.5) in Useplunk Plunk, published April 6, 2026. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 0.20%, the 10th percentile. No source names a fixed version.

References

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