# CVE-2026-123862: Node.js is vulnerable to a zlib denial of service via a stream destroy during a pending params() call

> A peer disconnecting during zlib streaming can crash Node.js processes that call deflate.params() while streaming.

- **Severity:** Low 2.9 (`CVSS:3.0/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Harmful if only installed:** No
- **Needs a specific call:** Yes (`zlib.params()`, `deflate.params()`)
- **Fix available:** Yes
- **Published:** 11 Nov 2026
- **Updated:** 11 Nov 2026
- **Also known as:** ALPINE-CVE-2026-123862, BELL-CVE-2026-123862, DEBIAN-CVE-2026-123862, GHSA-827v-4jh3-rppr, UBUNTU-CVE-2026-123862

## What is CVE-2026-123862?

CVE-2026-123862 is a low-severity denial of service vulnerability in nodejs node, published on 11 Nov 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

An uncatchable exception in the Node.js zlib streaming API lets a peer crash a process by disconnecting while data is being compressed. zlib.params() queues a flush and completes its work in that write's callback; if the stream is destroyed first, as pipeline() does when the peer goes away, Writable still invokes the callback with an error, but the callback ignores its arguments and asserts that the native handle still exists. The handle is gone, so an ERR_INTERNAL_ASSERTION is thrown from inside stream internals and bypasses the stream's error event, the params() callback, and the pipeline() callback, terminating the process. An application is affected only if it calls deflate.params() while streaming to a peer, which is uncommon. This vulnerability affects Node.js 26.x, 24.x, and 22.x.

Weakness: CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2026-123862?

An affected version is only exploitable if your software calls zlib.params() or deflate.params(). Many projects that include it are not exposed.


## How do I fix CVE-2026-123862?

No fix published yet.

## Is CVE-2026-123862 being exploited?

There is no known exploitation of CVE-2026-123862 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-123862 and fix it if it is affected.

What it is: CVE-2026-123862 is a low-severity denial of service vulnerability in nodejs node, published on 11 Nov 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-123862 in the wild and no public exploit code.
Exposure: An affected version is only exploitable if your software calls zlib.params() or deflate.params(). Many projects that include it are not exposed.

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.
   If an affected version is present, also search the code for calls to zlib.params() or deflate.params() and report whether any exist.
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-2026-123862/ (Markdown: https://insights.sbomify.com/CVE-2026-123862/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-123862
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-123862
- OSV: https://osv.dev/vulnerability/CVE-2026-123862

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-123862/
Summaries are generated and may contain mistakes; the official description above is the record.