CVE-2026-86250: Uncontrolled Resource Consumption in h3js h3
Description
h3 versions before 2.0.1-rc.18 fail to validate the chunk count parsed from user-controlled cookie values in setChunkedCookie() and deleteChunkedCookie() functions. Attackers can send a crafted cookie header with an extremely large chunk count to trigger an O(n²) cleanup loop that hangs the server process.
CVSS v4.0
Score 8.7high
Affected software
h3js
h3
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in h3 versions >=2.0.0-beta.4 and <2.0.1-rc.18 arises because the chunk count parsed from user-controlled cookie values is not validated in the setChunkedCookie() and deleteChunkedCookie() functions. This allows an attacker to supply a cookie header with a very large chunk count, triggering an O(n²) cleanup loop that can cause the server process to hang due to uncontrolled resource consumption.
Potential Impact
Successful exploitation can cause denial of service by hanging the server process, impacting availability. There is no indication of privilege escalation, data disclosure, or integrity compromise. The vulnerability has a CVSS 4.0 score of 8.7 (high severity), reflecting its potential to disrupt service remotely without authentication or user interaction.
Mitigation Recommendations
A fix is available in h3 version 2.0.1-rc.18 and later. Users should upgrade to this version or newer to remediate the vulnerability. No other mitigation or temporary workaround is indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-09-06T11:35:19.316Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a9d5b10acd9273b49b9c58a
Added to database: 09/06/2026, 12:22:40 UTC
Last enriched: 09/18/2026, 22:54:54 UTC
Last updated: 10/22/2026, 01:15:26 UTC
Views: 72
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