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01 Record

CVE-2026-53591

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

HighPUBLISHEDCNA: GitHub_M
CNA base score8.6 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L

02 Description

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

03 Exploitation and scoring

Exploitation
Public exploit code exists. CISA's assessment records a public proof of concept. That is not a report of exploitation in the wild.
SSVC decision
  • ExploitationpocPublic proof-of-concept exploit code exists. Not a report of exploitation in the wild.
  • AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
  • Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
0.26% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 18.2% of scored records. A rank, not a probability.
NVD base score
8.6 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L
NVD analysis status
Deferred. NVD last modified this record on 2026-10-24.
Red Hat severity
No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-07-20 19:47Z3 MO AGO
Last updated
2026-07-20 20:15Z3 MO AGO
Reserved
2026-06-09
Assigning CNA
GitHub_M
Record state
PUBLISHED
Severity
High (CVSS 8.6)
CNA CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:L
Weaknesses
  • CWE-287Improper AuthenticationClass
Data version
5.2
Document digest
157a76921a9a08a549f58451ab33ce1f6f8d9a8f247090878de6c608aeed1c1d

05 Affected products

VendorProductVersionsPlatforms
freescout-help-deskfreescout< 1.8.223—

06 References