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CVE-2026-44453

HIGH
7.5
CVSS 3.1
Description
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 6b5370d, h2o is vulnerable to a Denial of Service attack when calling alloca under certain conditions. When serving static files, h2o builds the file path on stack, by calling alloca. The maximum size of the memory allocated using alloca can be as huge as ~600KB, which exceeds the default pthread stack size used by musl libc (128KB). If the amount of memory allocated by alloca exceeds the stack size, the h2o server crashes with a segmentation fault, while it tries to touch the guard page. This issue has been fixed by commit 6b5370d.

Metadata

CVE ID
CVE-2026-44453
State
PUBLISHED
Assigner
GitHub_M
Reserved
2026-05-06 15:49 UTC
Published
2026-07-16 23:04 UTC
Last updated
2026-07-16 23:04 UTC
Primary CWE
CWE-789
CWE-789: Memory Allocation with Excessive Size Value
Vendor / Product
h2o / h2o
Sources
cve.org  ·  NVD

Severity & Metrics

7.5 HIGH CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Affected products (1)
VendorProductPlatformVersions
h2o h2o — < 6b5370d
Weakness (CWE)
CWESourceDescription
CWE-770 cna CWE-770: Allocation of Resources Without Limits or Throttling
CWE-789 cna CWE-789: Memory Allocation with Excessive Size Value
CVSS scores (1)
ScoreSeverityVersionSourceVector
7.5 HIGH 3.1 cna CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References (2)
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