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VULNERABILITIES

CVE-2026-55367 Details

Description

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 4212ce114506a073505fd389db16ad2ba4e582a0, a client could send an incomplete CONNECT-UDP Capsule with an excessively large declared length, causing H2O to keep buffering received bytes without a per-Capsule limit while waiting for the remainder. Deployments that enabled proxy.connect-udp and accepted CONNECT-UDP requests could exhaust server memory and lose availability. This vulnerability is fixed with commit 4212ce114506a073505fd389db16ad2ba4e582a0.

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:7.5 HIGHVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References to Advisories, Solutions, and Tools

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URLSource(s)Tag(s)
https://github.com/h2o/h2o/commit/4212ce114506a073505fd389db16ad2ba4e582a0 [email protected]
https://github.com/h2o/h2o/pull/3754 [email protected]
https://github.com/h2o/h2o/security/advisories/GHSA-q342-qp8v-p44c [email protected]

Weakness Enumeration

CWE-IDCWE NameSource
CWE-770Allocation of Resources Without Limits or Throttling[email protected]

Affected Products

No affected product data is available for this CVE.

Change History

2 change records found show changes

QUICK INFO

CVE Dictionary Entry:
CVE-2026-55367
NVD Published Date:
Nov 4, 2026
NVD Last Modified:
Nov 5, 2026
Source:
[email protected]
CVE-2026-55367 Details - Not Deferred