CVE-2026-86250CWE-400denial-of-service

CVE-2026-86250

High · published September 6, 2026

CVSS v3.1
7.5
EPSS
—
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS v4.0
8.7 · 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
EPSS
Not scored
Weakness
CWE-400 · Uncontrolled Resource Consumption
Published
2026-09-06T16:17Z
References (2)
https://github.com/h3js/h3/security/advisories/GHSA-q5pr-72pq-83v3 · [email protected]https://www.vulncheck.com/advisories/h3-before-2.0.1-rc.18-denial-of-service-via-unbounded-chunked-cookie · [email protected]
Timeline
  • 06 SEP 12:00Z
    h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie
    cvelistv5