HIGH 7.5 NVD
CVE-2026-55367
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
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.
References
- https://github.com/h2o/h2o/commit/4212ce114506a073505fd389db16ad2ba4e582a0
- https://github.com/h2o/h2o/pull/3754
- https://github.com/h2o/h2o/security/advisories/GHSA-q342-qp8v-p44c
This high severity vulnerability with a CVSS score of 7.5 was published on 2026-11-04 via NVD.
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