CVE-2026-44453h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3.
Updated under an hour ago ()
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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.
- CVSS
- 7.5 HIGH (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-770, CWE-789
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Analyzed
- Record last updated
- Aug 6, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
h2o h2o h2o:h2o | before 2026-05-29 | NVD |
References
- https://github.com/h2o/h2o/commit/6b5370d9d09fcf83aa7620ddf77de1954a192181patch
- https://github.com/h2o/h2o/security/advisories/GHSA-rf9v-m59p-mq84vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.