CVE-2025-66020Public exploitNetwork attack vector

Application hang via overlapping emoji character classes

Published Nov 26, 2025 · Updated Nov 26, 2025

ReDoS in the emoji action in Open Circle Valibot 0.31.0 through 1.1.0 allows remote attackers to hang applications via crafted input. EMOJI_REGEX contains overlapping Emoji_Presentation, regional-indicator, and Emoji_Modifier_Base alternatives, causing exponential backtracking on a near-match. Exposure requires an application to pass attacker-controlled input to emoji validation; one short request can monopolize CPU and block its event loop.

CVSS severity7.5
High
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

ReDoS in the emoji action in Open Circle Valibot 0.31.0 through 1.1.0 allows remote attackers to hang applications via crafted input. EMOJI_REGEX contains overlapping Emoji_Presentation, regional-indicator, and Emoji_Modifier_Base alternatives, causing exponential backtracking on a near-match. Exposure requires an application to pass attacker-controlled input to emoji validation; one short request can monopolize CPU and block its event loop.

The record

CVE
CVE-2025-66020
Published
Nov 26, 2025
Updated
Nov 26, 2025
Vendor
Open Circle
Product
Valibot
Classifications
CWE-1333, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 26, 2025CVE publishedPublication date reported by the CVE source.
  2. Nov 26, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 0.31.0, < 1.2.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Open Circle · Valibotversion=>= 0.31.0, < 1.2.0

Published CVSS scores

7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo