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.
Metrics
Affected Vendors & Products
References
History
Fri, 17 Jul 2026 15:30:00 +0000
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ssvc
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Fri, 17 Jul 2026 00:45:00 +0000
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| First Time appeared |
H2o
H2o h2o |
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| Vendors & Products |
H2o
H2o h2o |
Thu, 16 Jul 2026 23:15:00 +0000
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| 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. | |
| Title | h2o is vulnerable to musl libc stack overflow | |
| Weaknesses | CWE-770 CWE-789 |
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| References |
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| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-07-17T14:29:15.447Z
Reserved: 2026-05-06T15:49:25.192Z
Link: CVE-2026-44453
Updated: 2026-07-17T14:29:11.407Z
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OpenCVE Enrichment
Updated: 2026-07-17T00:30:03Z