CVE-2026-54340

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Source
https://cve.org/CVERecord?id=CVE-2026-54340
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-54340.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-54340
Aliases
  • GHSA-qcrr-wrhc-pgq9
Downstream
Published
2026-07-16T23:29:50Z
Modified
2026-10-28T02:30:24Z
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
h2o has HTTP/2 state amplification
Details

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 9265bdd, there is an HTTP/2 state amplification issue that combines HPACK decompression amplification with Slowloris-style stream stalling. Amplified decoded header state can be retained by stalled HTTP/2 streams, and depending on the configuration, additional limits are needed to bound decoded header state and prevent attack. This issue has been fixed by commit 9265bdd.

Database specific 
{
    "cna_assigner":  "GitHub_M",
    "cwe_ids":  [
        "CWE-400",
        "CWE-770"
    ],
    "osv_generated_from":  "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54340.json",
    "unresolved_ranges":  [
        {
            "extracted_events":  [
                {
                    "range":  [
                        {
                            "fixed":  "9265bdd"
                        }
                    ],
                    "source":  "AFFECTED_FIELD",
                    "strategy":  "StringRangeExpression"
                }
            ]
        }
    ]
}
References

Affected packages

Git / github.com/h2o/h2o

Affected ranges

Type
GIT
Repo
https://github.com/h2o/h2o
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
9265bdd
Fixed
9265bdd9a996ed992681055e3996baf3e09d2063
Database specific
Show details 
{
    "extracted_events":  [
        {
            "range":  [
                {
                    "introduced":  "0"
                },
                {
                    "fixed":  "9265bdd"
                }
            ],
            "source":  "DESCRIPTION"
        },
        {
            "range":  [
                {
                    "fixed":  "9265bdd9a996ed992681055e3996baf3e09d2063"
                }
            ],
            "source":  "REFERENCES_COMMIT"
        }
    ]
}
Type
GIT
Repo
https://github.com/h2oai/h2o-3
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
9265bdd
Database specific
Show details 
{
    "extracted_events":  [
        {
            "range":  [
                {
                    "introduced":  "0"
                },
                {
                    "fixed":  "9265bdd"
                }
            ],
            "source":  "DESCRIPTION"
        }
    ]
}

Affected versions

v0.*
v0.9.1
v0.9.2
v1.*
v1.0.1
v1.1.0
v1.1.1
v1.2.0
v1.3.0
v1.3.0-beta1
v1.3.1
v1.4.0
v1.4.1
v1.4.2
v1.5.0
v1.5.0-beta1
v1.5.0-beta2
v1.5.0-beta3
v1.5.0-beta4
v1.5.1
v1.5.2
v1.5.3
v1.6.0
v1.6.0-beta1
v1.6.0-beta2
v1.7.0
v1.7.0-beta1
v1.7.0-beta2
v1.7.0-beta3
v1.7.0-beta4
v1.7.0-beta5

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-54340.json"