Inefficient regular expression complexity in Valibot - CVE-2025-66020
Published: April 28, 2026
Vulnerability identifier: #VU128350
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2025-66020
CWE-ID: CWE-1333
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Open Circle
Affected software:
Valibot
Valibot
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to inefficient regular expression complexity in EMOJI_REGEX used by the emoji action when processing user-controllable input. A remote attacker can submit a specially crafted short string to cause a denial of service.
The issue is caused by catastrophic backtracking due to overlapping character classes in the regex pattern.
How to mitigate CVE-2025-66020
Install security update from vendor's website.