CVE-2026-53591
FreeScout Vulnerable to Unauthenticated Conversation Thread Injection via HMAC Length Bypass in FetchEmails
- State
- Published
- Severity
- 8.6 High
- Published
- Jul 20, 2026
- Updated
- Jul 20, 2026
- Reserved
- Jun 9, 2026
Description
FreeScout is a free help desk and shared inbox built with PHP's Laravel framework. Prior to version 1.8.223, an unauthenticated attacker can inject messages into any existing support conversation by sending a single email to the helpdesk's public address with a crafted `In-Reply-To` header. No credentials, tokens, or prior access are required. The injected message is rendered in the agent UI as a legitimate customer reply, the conversation is automatically reopened, and the `last_reply_from` field is set to the attacker's identity. Version 1.8.223 contains a fix.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 8.6 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L | GitHub_M |
Weaknesses
- CWE-287 Improper Authentication
Affected Products
| Product | Versions |
|---|---|
freescoutfreescout-help-desk |
|
References
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