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CVE-2026-86250

h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie

CVSS 4.0 8.7 HIGHCVSS 3.1 7.5 HIGHCheck source for fixed versionsKEV status unknown

Original advisory

Historical advisory recorded 23 Oct 2026 15:48:27 UTC. Read the latest advisory.

cve-program · CVE-2026-86250

Published

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.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-86250

Published

h3

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "h3js",
                    "product": "h3",
                    "defaultStatus": "unaffected",
                    "packageURL": "pkg:npm/h3",
                    "versions": [
                        {
                            "version": "2.0.0-beta.4",
                            "status": "affected",
                            "versionType": "semver",
                            "lessThan": "2.0.1-rc.18"
                        },
                        {
                            "version": "2.0.1-rc.18",
                            "status": "unaffected",
                            "versionType": "semver"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON