Overview
CVE-2025-66020 is a high-severity vulnerability affecting the Valibot data validation library. Specifically, it’s a Regular Expression Denial of Service (ReDoS) vulnerability found within the EMOJI_REGEX used in the emoji validation action. This flaw allows attackers to craft relatively short input strings (less than 100 characters) that can cause the regular expression engine to consume excessive CPU time, potentially leading to a Denial of Service (DoS) condition for applications utilizing the vulnerable Valibot versions.
The affected versions of Valibot are those ranging from 0.31.0 to 1.1.0. A patch addressing this issue is available in version 1.2.0.
Technical Details
The vulnerability stems from the complexity of the EMOJI_REGEX used to validate emoji characters. Maliciously crafted input, particularly those containing specific sequences of characters, can trigger catastrophic backtracking within the regex engine. This backtracking leads to exponential time complexity, effectively stalling the CPU and rendering the application unresponsive. The impact is significant because even a small number of such requests can overwhelm the server, resulting in a DoS.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) assigns this vulnerability a score of 7.5, classifying it as HIGH severity. This score reflects the potential for significant impact and the relative ease of exploitation. The primary metric contributing to this score is the availability impact, as successful exploitation leads to a denial of service.
Possible Impact
A successful exploit of CVE-2025-66020 can have severe consequences:
- Denial of Service (DoS): The most direct impact is a DoS attack, where the application becomes unavailable to legitimate users due to excessive CPU consumption.
- Resource Exhaustion: The vulnerability can lead to resource exhaustion, potentially impacting other services running on the same server.
- Reputational Damage: Downtime and service disruptions can damage the reputation of organizations relying on the vulnerable library.
Mitigation and Patch Steps
The recommended mitigation is to upgrade to Valibot version 1.2.0 or later. This version includes a patch that resolves the ReDoS vulnerability in the EMOJI_REGEX. If upgrading is not immediately feasible, consider implementing input validation and sanitization measures to limit the length and complexity of input strings being processed by the vulnerable emoji validation. However, this should be considered a temporary workaround and not a replacement for upgrading.
References
Valibot Commit: cfb799db301a953a0950d5c05a34a3ab121262dc
Valibot Security Advisory: GHSA-vqpr-j7v3-hqw9
