Internal network scanning via unvalidated mail hosts
Published Apr 21, 2026 · Updated Apr 21, 2026
SSRF in FreeScout before 1.8.213 allows remote authenticated users with administrator access to probe internal hosts and ports. MailboxesController passes stored IMAP and SMTP host and port values to fsockopen and protocol clients without destination validation, then exposes connection differences and IMAP debug output. Administrator access and server reachability to the target are required; the result is internal port scanning, service fingerprinting, and limited response disclosure.
Summary
What happened
SSRF in FreeScout before 1.8.213 allows remote authenticated users with administrator access to probe internal hosts and ports. MailboxesController passes stored IMAP and SMTP host and port values to fsockopen and protocol clients without destination validation, then exposes connection differences and IMAP debug output. Administrator access and server reachability to the target are required; the result is internal port scanning, service fingerprinting, and limited response disclosure.
The record
- CVE
- CVE-2026-40566
- Published
- Apr 21, 2026
- Updated
- Apr 21, 2026
- Vendor
- FreeScout
- Product
- FreeScout
- Classifications
- CWE-918, T1046
- Attack vector
- network
- Privileges
- admin
Timeline
How it unfolded
- Apr 21, 2026CVE publishedPublication date reported by the CVE source.
- 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.
- Affected versionversion=< 1.8.213
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Public exploit references
- Upstream IMAP/SMTP connection-test proof of conceptproof of concept · unverified
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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