CVE-2026-86250
h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie
- State
- Published
- Severity
- 8.7 High
- Published
- Sep 6, 2026
- Updated
- Sep 18, 2026
- Reserved
- Sep 6, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | 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 | VulnCheck |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | VulnCheck |
Weaknesses
- CWE-400 Uncontrolled Resource Consumption
Affected Products
| Product | Versions |
|---|---|
h3h3js |
|
References
- GitHub Security Advisory (GHSA-q5pr-72pq-83v3)vendor-advisory
- VulnCheck Advisory: h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookiethird-party-advisory
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