CVE-2026-40567Public exploitNetwork attack vector

Outgoing email HTML injection via unescaped customer name

Published Apr 21, 2026 · Updated Apr 21, 2026

HTML injection in FreeScout before 1.8.213 allows remote attackers to alter outgoing support emails via crafted From display names. Inbound IMAP processing stores the name without sanitization, and signature rendering reconstructs it and emits the customer-name variable without HTML escaping. Exploitation requires a monitored mailbox, a signature using that variable, and an agent reply; injected links, tracking pixels, or spoofed content then appear in legitimate support email.

CVSS severity5.8
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTML injection in FreeScout before 1.8.213 allows remote attackers to alter outgoing support emails via crafted From display names. Inbound IMAP processing stores the name without sanitization, and signature rendering reconstructs it and emits the customer-name variable without HTML escaping. Exploitation requires a monitored mailbox, a signature using that variable, and an agent reply; injected links, tracking pixels, or spoofed content then appear in legitimate support email.

The record

CVE
CVE-2026-40567
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
FreeScout
Product
FreeScout
Classifications
CWE-116, T1566.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 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=< 1.8.213

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FreeScout · FreeScoutversion=< 1.8.213

Published CVSS scores

5.8GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-116Improper Encoding or Escaping of Output
T1566.002Spearphishing Link

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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