Description
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1, when h2o processes a QPACK instruction sent from the peer over HTTP/3, lib/http3/qpack.c might allocate an on-stack buffer as large as approximately 800 KB by calling alloca, which exceeds the default pthread stack size used by musl libc and causes the h2o server to crash with a segmentation fault while touching the guard page. This issue is fixed in commit edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1.
References (2)
Core 2
Core References
X_Refsource_Confirm x_refsource_confirm
https://github.com/h2o/h2o/security/advisories/GHSA-432c-8xmj-frmq
X_Refsource_Misc x_refsource_misc
https://github.com/h2o/h2o/commit/edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1
Scores
CVSS v3
7.5
EPSS
0.0034
EPSS Percentile
27.0%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CISA SSVC
Vulnrichment
Exploitation
none
Automatable
yes
Technical Impact
partial
Details
CWE
CWE-789
Status
published
Products (1)
h2o/h2o
< edd7a120bfc4af11ac0cbebce2a43cc1f93f9af1
Published
Jul 10, 2026
Tracked Since
Jul 11, 2026