Stack-based buffer overflow in h2o - CVE-2026-55213
Published: July 1, 2026
Vulnerability identifier: #VU136036
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-55213
CWE-ID: CWE-121
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: h2o
Affected software:
h2o
h2o
Detailed vulnerability description
The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.
The vulnerability exists due to a boundary error within QPACK. A remote unauthenticated attacker can trigger stack-based buffer overflow and cause a denial of service condition on the target system.
How to mitigate CVE-2026-55213
Install updates from vendor's website.