{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-53591","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-06-09T19:11:53.485Z","datePublished":"2026-07-20T19:47:18.338Z","dateUpdated":"2026-07-20T20:15:26.874Z"},"containers":{"cna":{"title":"FreeScout Vulnerable to Unauthenticated Conversation Thread Injection via HMAC Length Bypass in FetchEmails","problemTypes":[{"descriptions":[{"cweId":"CWE-287","lang":"en","description":"CWE-287: Improper Authentication","type":"CWE"}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":8.6,"baseSeverity":"HIGH","confidentialityImpact":"LOW","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L","version":"3.1"}}],"references":[{"name":"https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-8vm3-wwq4-ggfx","tags":["x_refsource_CONFIRM"],"url":"https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-8vm3-wwq4-ggfx"}],"affected":[{"vendor":"freescout-help-desk","product":"freescout","versions":[{"version":"< 1.8.223","status":"affected"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-07-20T19:47:18.338Z"},"descriptions":[{"lang":"en","value":"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."}],"source":{"advisory":"GHSA-8vm3-wwq4-ggfx","discovery":"UNKNOWN"}},"adp":[{"references":[{"url":"https://github.com/freescout-help-desk/freescout/security/advisories/GHSA-8vm3-wwq4-ggfx","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-07-20T20:15:06.613729Z","id":"CVE-2026-53591","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-07-20T20:15:26.874Z"}}]}}