Auth bypass in Freescout-Help-Desk Freescout
CVE-2026-53591
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.
Vulnerability class: Broken Authentication
EPSS: 0.004 (30.5th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L.
Affected products
- Freescout-help-desk Freescout — versions < 1.8.223
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
Frequently asked questions
- What is CVE-2026-53591?
- CVE-2026-53591 is a high-severity vulnerability in Freescout-Help-Desk Freescout, classified under Improper Authentication. CVSS score: 8.6/10. Published 2026-07-20.
- How severe is CVE-2026-53591?
- High severity. CVSS v3 base score is 8.6 out of 10.