CVE-2026-44436

Source
https://cve.org/CVERecord?id=CVE-2026-44436
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-44436.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-44436
Aliases
  • GHSA-v55w-59qx-2v78
Published
2026-07-16T22:44:34Z
Modified
2026-08-12T03:51:24Z
Severity
  • 7.5 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CVSS Calculator
Summary
Quicly is vulnerable to connection state corruption
Details

Quicly is an IETF QUIC protocol implementation intended primarily for use within the H2O HTTP server. Prior to commit 8b178e6, Quicly is vulnerable to a Denial of Service attack through connection state corruption. In QUIC Invariants, the maximum length of a Connection ID is 255 bytes, while QUIC version 1 further restricts the maximum to 20 bytes. Quicly implements QUIC version 1 and therefore its CID buffers are limited to 20 bytes. However, to be able to respond to unknown versions of QUIC, its packet decoder accepts Connection IDs of up to 255 bytes. As its CID buffers are merely 20 bytes long, Quicly must reject QUIC version 1 packets with Connection IDs longer than that. The command line tool bundled with Quicly has had that check, however the library itself lacked such enforcement. As a consequence, when used by applications that lack their own enforcement, the connection state becoming inconsistent to buffer overrun. Fortunately, the overflow stops within the allocated chunk of memory, but nevertheless, the bug leads to assertion failures. This issue has been fixed by commit 8b178e6.

Database specific
{
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
        "CWE-120",
        "CWE-787"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44436.json",
    "unresolved_ranges": [
        {
            "extracted_events": [
                {
                    "fixed": "8b178e6"
                }
            ],
            "source": "AFFECTED_FIELD"
        }
    ]
}
References

Affected packages

Git / github.com/h2o/quicly

Affected ranges

Type
GIT
Repo
https://github.com/h2o/quicly
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
Database specific
Show details
{
    "source": "REFERENCES"
}

Database specific

source
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-44436.json"