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TI-2026-38648 Aliases CVE-2026-53591

FreeScout Vulnerable to Unauthenticated Conversation Thread Injection via HMAC Length Bypass in FetchEmails

Priority HIGH 76CWE-287Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
Low · High · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-287.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00265 18th percentileScored 2026-11-07
Fix Fixed freescout (freescout-help-desk): 1.8.223

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
freescout-help-deskfreescoutbefore 1.8.2231.8.223Patch availableCNA
  • freescout Vendorfreescout-help-desk Affected before 1.8.223 Fixed in 1.8.223 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:freescout:freescout:*:*:*:*:*:*:*:*——freescout-help-desk

Remediation

  • Fix · CNA freescout (freescout-help-desk) Fixed in 1.8.223

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-53591

References

Other 1

  • TI-2026-38652 FreeScout vulnerable to anonymous account takeover via /user-setup empty invite_hash on MySQL CVSS 3.1CRITICAL 9.4
  • TI-2026-22019 FreeScout's Predictable Authentication Token Enables Account Takeover CVSS 3.1CRITICAL 9.8
  • TI-2026-30304 FreeScout's user invitation hash never expires: permanent unauthenticated account takeover if invite link leaks CVSS 3.1CRITICAL 9.1
  • TI-2026-29249 FreeScout has Authentication Bypass and Information Disclosure in SystemController via /system/cron CVSS 4.0HIGH 8.9
  • TI-2026-29247 FreeScout has Predictable Attachment Token that Allows Unauthenticated Private File Download via Brute Force CVSS 4.0HIGH 8.8
  • TI-2026-25245 FreeScout: Stored XSS via Unescaped Email Template Rendering ({!! $thread->body !!}) CVSS 3.1CRITICAL 9.3
See all 90 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences