CVE-2026-44433
5.3 · MEDIUMOverview
CVE-2026-44433 is a medium-severity vulnerability affecting h2o quicly. It was published on July 16, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 8b178e6, an adversarial peer could send a STREAM frame carrying just one byte at the largest offset being permitted to obtain additional flow control credit, which under certain circumstances could lead to a Denial of Service. Assuming the application prepares a receive buffer for storing all data that arrive out-of-order, up to the largest offset being received, this behavior could lead to the application allocating large amount of memory with the peer sending only a handful of packets, resulting in memory exhaustion. In addition to the receive buffer allocation strategy, the severity of this vulnerability depends on how the application controls the stream concurrency. In case of the H2O HTTP server, under its default setting, this bug increases the maximum amount of memory allocated per connection by about 4 times. This issue has been fixed by commit 8b178e6.
Remediation
Check the references section for vendor advisories and patches from h2o. Update quicly to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| h2o | quicly | >= 0, < 2026-05-29 | Affected |
Frequently Asked Questions
What is CVE-2026-44433?
CVE-2026-44433 is a medium-severity vulnerability affecting h2o quicly. It was published on July 16, 2026 and has a CVSS 3.1 base score of 5.3 (MEDIUM).
How severe is CVE-2026-44433?
This vulnerability has a CVSS 3.1 base score of 5.3, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-44433?
Check the references section for vendor advisories and patches from h2o. Update quicly to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-44433?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-44433 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
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