# CVE-2026-123863: Node.js is vulnerable to a remote HTTP/2 denial of service via a reachable assertion in Http2Session teardown

Status: published. Published: 2026-11-11. Updated: 2026-11-11.

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).

## Remediation

No remediation reported in collected sources

## Affected products and versions

- nodejs / node: ≥ 24.0.0; < 24.22.3 (affected, semver); ≥ 25.0.0; < 26.13.1 (affected, semver). Source: CNA: openjs

## Severity and prioritization

- CVSS 3.0: 8.2 (high); CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H; source: CNA: openjs

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-617

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://nodejs.org/en/blog/vulnerability/november-2026-security-releases (CNA: openjs; vendor-advisory)

- https://cna.openjsf.org/security-advisories.html (CNA: openjs)

## Provenance

- CNA: openjs: https://www.cve.org/CVERecord?id=CVE-2026-123863; retrieved 2026-11-11; source updated 2026-11-11

Revision: 9044f1db76402cde6a35df3070b7176b9b948add252927080a427893afd36a26

Canonical: https://y2.dev/cve/CVE-2026-123863

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