CVE-2026-54340

{"id": "CVE-2026-54340", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-54340", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-07-17T15:26:10.914862Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "security-advisories@github.com", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.5, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 3.9}]}, "affected": [{"source": "security-advisories@github.com", "affectedData": [{"vendor": "h2o", "product": "h2o", "versions": [{"status": "affected", "version": "< 9265bdd"}]}]}], "published": "2026-07-17T00:16:25.810", "references": [{"url": "https://github.com/h2o/h2o/commit/9265bdd9a996ed992681055e3996baf3e09d2063", "source": "security-advisories@github.com"}, {"url": "https://github.com/h2o/h2o/security/advisories/GHSA-qcrr-wrhc-pgq9", "source": "security-advisories@github.com"}], "vulnStatus": "Undergoing Analysis", "weaknesses": [{"type": "Secondary", "source": "security-advisories@github.com", "description": [{"lang": "en", "value": "CWE-400"}, {"lang": "en", "value": "CWE-770"}]}], "descriptions": [{"lang": "en", "value": "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."}], "lastModified": "2026-07-17T19:17:17.030", "sourceIdentifier": "security-advisories@github.com"}