stoatchat before 0.15.5 fails to revalidate usernames after Unicode sanitization, allowing attackers to create usernames with forbidden characters by submitting Unicode letters that transform into rejected characters. Attackers can bypass character allowlists and length limits to create reserved-name lookalikes, embed special characters, and exceed the 32-character storage limit.
CVSS Details
- CVSS 4.0 Base Score: 5.3 (MEDIUM)
- CVSS 4.0 Vector: (CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X)
- CVSS 3.1 Base Score: 4.3
- CVSS 3.1 Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N)
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