# CVE-2026-123866: Node.js is vulnerable to HTTP/2 response memory disclosure via a use-after-free during stream teardown

> A remote peer can make Node.js HTTP/2 servers leak response memory, including other connections' buffers, to a peer; Node.js HTTP/2 operators should care.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Harmful if only installed:** No
- **Needs a specific call:** No
- **Fix available:** Yes
- **Published:** 11 Nov 2026
- **Updated:** 11 Nov 2026
- **Also known as:** ALPINE-CVE-2026-123866, BELL-CVE-2026-123866, DEBIAN-CVE-2026-123866, GHSA-52jx-xggf-7f6v, UBUNTU-CVE-2026-123866

## What is CVE-2026-123866?

CVE-2026-123866 is a high-severity use after free vulnerability in nodejs node, published on 11 Nov 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A use-after-free in Node.js HTTP/2 stream teardown can leak response memory, including the contents of other connections' response buffers, to a peer. When a stream is torn down while a write is still backpressured, for example by a peer RST_STREAM or by the server's own per-stream timeout destroying the stream, the stream's response buffer is freed but a reference to it is still used, so freed or unrelated heap memory is written to the socket instead of the intended response. On Node.js 26.x and 24.x the teardown can be driven purely by a remote peer once the window-size change from 26.9.0 and 24.22.0 is present, and on all supported lines the same defect is reachable through an application-initiated teardown such as a per-stream idle timeout. This vulnerability affects Node.js 26.x, 24.x, and 22.x.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-123866?

An affected version is exposed as installed. No special setting or call is needed.


## How do I fix CVE-2026-123866?

Upgrade to a fixed version.

## Is CVE-2026-123866 being exploited?

There is no known exploitation of CVE-2026-123866 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-123866 and fix it if it is affected.

What it is: CVE-2026-123866 is a high-severity use after free vulnerability in nodejs node, published on 11 Nov 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-123866 in the wild and no public exploit code.
Exposure: An affected version is exposed as installed. No special setting or call is needed.

Affected product: nodejs node. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-123866/ (Markdown: https://insights.sbomify.com/CVE-2026-123866/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-123866
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-123866
- OSV: https://osv.dev/vulnerability/CVE-2026-123866

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-123866/
Summaries are generated and may contain mistakes; the official description above is the record.