HomeVulnerabilityMail2Shell zero-click assault lets hackers hijack FreeScout mail servers

Mail2Shell zero-click assault lets hackers hijack FreeScout mail servers

A most severity vulnerability within the FreeScout helpdesk platform permits hackers to attain distant code execution with none person interplay or authentication.

The flaw is tracked as CVE-2026-28289 and bypasses a repair for an additional distant code execution (RCE) security concern (CVE-2026-27636) that could possibly be exploited by authenticated customers with add permissions.

Researchers at OX Safety, an organization that secures functions from code to runtime, say that an attacker can exploit the brand new vulnerability by “sending a single crafted e mail to any deal with configured in FreeScout.”

In keeping with them, the repair tried to dam harmful file uploads by modifying filenames with restricted extensions or these beginning with a dot.

The OX Analysis workforce found {that a} zero-width house (Unicode U+200B) could possibly be positioned earlier than the filename to bypass the not too long ago launched validation mechanism, for the reason that character shouldn’t be handled as seen content material.

Subsequent processing removes that character, permitting the file to be saved as a dotfile, and therefore, nonetheless triggering CVE-2026-27636 exploitation by fully bypassing the most recent security checks.

The exploitation chain
The exploitation chain
Supply: OX Analysis

Making issues worse, CVE-2026-28289 will be triggered by a malicious e mail attachment delivered to a mailbox configured in FreeScout, the researchers say.

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This system shops the attachment in “/storage/attachment/…,” enabling the attacker to entry the uploaded payload via the net interface and execute instructions on the server with out authentication or person interplay, making it a zero-click vulnerability.

“A patch bypass vulnerability in FreeScout 1.8.206 permits any authenticated person with file add permissions to attain Distant Code Execution (RCE) on the server by importing a malicious .htaccess file utilizing a zero-width house character prefix to bypass the security verify,” the seller says in a security bulletin.

FreeScout is an open-source assist desk and shared mailbox platform utilized by organizations to handle buyer help emails and tickets. It’s a self-hosted various to Zendesk or Assist Scout.

The venture’s GitHub repository has 4,100 stars and over 620 forks, and OX Analysis experiences that its Shodan scans returned 1,100 publicly uncovered cases, indicating it’s a extensively used answer.

CVE‑2026‑28289 impacts all FreeScout variations as much as and together with 1.8.206 and was patched in model 1.8.207, launched 4 days in the past.

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The FreeScout workforce warned that profitable exploitation of CVE‑2026‑28289 could end in full server compromise, data breaches, lateral motion into inner networks, and repair disruption. Therefore, fast patching is suggested.

OX Analysis has additionally really useful disabling ‘AllowOverrideAll’ within the Apache configuration on the FreeScout server, even when on model 1.8.207.

No lively exploitation of CVE‑2026‑28289 has been noticed within the wild as of scripting this, however given the character of this flaw, the hazard of malicious exercise beginning quickly could be very excessive.

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