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A client can arrange for an `Http2Stream` that still holds `nghttp2`-allocated header buffers to outlive its session: the stream is removed from the session's stream set but never detached, so when `~Http2Session()` runs the memory accounting is nonzero and the `CHECK_EQ(current_nghttp2_memory_, 0)` assertion fails, terminating the process. The trigger needs only a default `http2` server whose handler responds before the request body has ended, which is typical. It is a variant of CVE-2024-27983 that the earlier fix did not cover, because that fix only detached streams still tracked in the session. This vulnerability affects Node.js 26.x (since 26.9.0) and 24.x (since 24.22.0)."}],"value":"A reachable assertion in Node.js HTTP/2 session teardown lets any unauthenticated client abort the server, over both TLS and cleartext. 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This vulnerability affects Node.js 26.x (since 26.9.0) and 24.x (since 24.22.0)."}],"metrics":[{"cvssV3_0":{"baseScore":8.2,"baseSeverity":"HIGH","vectorString":"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H","version":"3.0"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-617","description":"Reachable Assertion","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-11-11T18:16:12.733Z","orgId":"ce714d77-add3-4f53-aff5-83d477b104bb","shortName":"openjs"},"references":[{"tags":["vendor-advisory"],"url":"https://nodejs.org/en/blog/vulnerability/november-2026-security-releases"},{"url":"https://cna.openjsf.org/security-advisories.html"}],"title":"Node.js is vulnerable to a remote HTTP/2 denial of service via a reachable assertion in Http2Session teardown","x_generator":{"engine":"nodejs-private/security-release publish-cves"}}},"cveMetadata":{"assignerOrgId":"ce714d77-add3-4f53-aff5-83d477b104bb","assignerShortName":"openjs","cveId":"CVE-2026-123863","datePublished":"2026-11-11T18:16:12.733Z","dateReserved":"2026-11-06T16:12:44.473Z","dateUpdated":"2026-11-11T18:16:12.733Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-11-11 19:17:32","lastModifiedDate":"2026-11-11 19:17:32","problem_types":["CWE-617","CWE-617 Reachable Assertion"],"metrics":{"cvssMetricV30":[{"source":"ce714d77-add3-4f53-aff5-83d477b104bb","type":"Secondary","cvssData":{"version":"3.0","vectorString":"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H","baseScore":8.2,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"LOW","availabilityImpact":"HIGH"},"exploitabilityScore":3.9,"impactScore":4.2}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"123863","Ordinal":"1","Title":"Node.js is vulnerable to a remote HTTP/2 denial of service via a","CVE":"CVE-2026-123863","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"123863","Ordinal":"1","NoteData":"A reachable assertion in Node.js HTTP/2 session teardown lets any unauthenticated client abort the server, over both TLS and cleartext. A client can arrange for an Http2Stream that still holds nghttp2-allocated header buffers to outlive its session: the stream is removed from the session's stream set but never detached, so when ~Http2Session() runs the memory accounting is nonzero and the CHECK_EQ(current_nghttp2_memory_, 0) assertion fails, terminating the process. The trigger needs only a default http2 server whose handler responds before the request body has ended, which is typical. It is a variant of CVE-2024-27983 that the earlier fix did not cover, because that fix only detached streams still tracked in the session. This vulnerability affects Node.js 26.x (since 26.9.0) and 24.x (since 24.22.0).","Type":"Description","Title":"Node.js is vulnerable to a remote HTTP/2 denial of service via a"}]}}}