CVE-2026-34975Public exploitNetwork attack vector

Authenticated email header injection via raw MIME interpolation

Published Apr 6, 2026 · Updated Apr 6, 2026

CRLF injection in SESService.ts in Plunk before 0.8.0 allows remote authenticated users to inject email headers through the send API. Raw MIME construction directly interpolates from.name, subject, custom header keys and values, and attachment filenames without rejecting carriage returns or line feeds. A valid API key and verified sender domain suffice to add Bcc or Reply-To headers, silently copy messages, redirect replies, or spoof sender identity.

CVSS severity8.5
High
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CRLF injection in SESService.ts in Plunk before 0.8.0 allows remote authenticated users to inject email headers through the send API. Raw MIME construction directly interpolates from.name, subject, custom header keys and values, and attachment filenames without rejecting carriage returns or line feeds. A valid API key and verified sender domain suffice to add Bcc or Reply-To headers, silently copy messages, redirect replies, or spoof sender identity.

The record

CVE
CVE-2026-34975
Published
Apr 6, 2026
Updated
Apr 6, 2026
Vendor
Plunk
Product
Plunk
Classifications
CWE-93, T1565.002
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 6, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Plunk · Plunkversion=< 0.8.0

Published CVSS scores

8.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-93Improper Neutralization of CRLF Sequences ('CRLF Injection')
T1565.002Transmitted Data Manipulation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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