CVE-2026-53591: CWE-287: Improper Authentication in freescout-help-desk freescout
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.
AI Analysis
Technical Summary
CVE-2026-53591 is an improper authentication vulnerability (CWE-287) in FreeScout help desk software before version 1.8.223. An attacker can send a single crafted email to the public helpdesk address with a manipulated In-Reply-To header to inject messages into any existing support conversation without any credentials or prior access. The injected message is displayed in the agent UI as if it were a legitimate customer reply, reopening the conversation and modifying the last_reply_from field to the attacker's identity. This could mislead support agents and disrupt support workflows. The vulnerability has a CVSS 3.1 base score of 8.6 (high severity), reflecting network attack vector, no privileges or user interaction required, and impacts integrity and availability.
Potential Impact
An unauthenticated attacker can inject arbitrary messages into existing support conversations, causing false customer replies to appear in the agent interface. This can mislead support staff, disrupt normal support operations, and potentially cause incorrect handling of support tickets. The integrity of conversation data is compromised, and conversations are automatically reopened, affecting availability of the support workflow.
Mitigation Recommendations
Upgrade FreeScout to version 1.8.223 or later, which contains a fix for this vulnerability. No other mitigations are indicated. Patch status is not explicitly stated but the vendor has released version 1.8.223 as the fixed version.
CVE-2026-53591: CWE-287: Improper Authentication in freescout-help-desk freescout
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.
CVSS v3.1
Score 8.6high
Affected software
pkg:github/freescout-help-desk/freescoutRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-53591 is an improper authentication vulnerability (CWE-287) in FreeScout help desk software before version 1.8.223. An attacker can send a single crafted email to the public helpdesk address with a manipulated In-Reply-To header to inject messages into any existing support conversation without any credentials or prior access. The injected message is displayed in the agent UI as if it were a legitimate customer reply, reopening the conversation and modifying the last_reply_from field to the attacker's identity. This could mislead support agents and disrupt support workflows. The vulnerability has a CVSS 3.1 base score of 8.6 (high severity), reflecting network attack vector, no privileges or user interaction required, and impacts integrity and availability.
Potential Impact
An unauthenticated attacker can inject arbitrary messages into existing support conversations, causing false customer replies to appear in the agent interface. This can mislead support staff, disrupt normal support operations, and potentially cause incorrect handling of support tickets. The integrity of conversation data is compromised, and conversations are automatically reopened, affecting availability of the support workflow.
Mitigation Recommendations
Upgrade FreeScout to version 1.8.223 or later, which contains a fix for this vulnerability. No other mitigations are indicated. Patch status is not explicitly stated but the vendor has released version 1.8.223 as the fixed version.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-09T19:11:53.485Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a5e7dae2a4a8d5989a50dfc
Added to database: 07/20/2026, 19:57:34 UTC
Last enriched: 07/20/2026, 20:12:14 UTC
Last updated: 07/21/2026, 03:49:58 UTC
Views: 11
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