CVE-2026-87029 undici vulnerable to Denial of Service via unhandled exception in the decompress interceptor
A malicious server can crash Node.js applications using undici by triggering an unhandled exception in the decompress interceptor when combined with size-limiting handlers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-87029?
CVE-2026-87029 is a medium-severity denial of service vulnerability in Nodejs Undici, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
undici is an HTTP client library for Node.js. In versions 7.15.0 through 7.30.0 and 8.0.0 through 8.12.1, its decompress interceptor forwards decompressed response data to the downstream handler from zlib stream event callbacks without catching exceptions those callbacks may throw, and while undici's engine converts a synchronous throw from a downstream handler into a per-request failure, that protection is absent when the throw happens asynchronously from a zlib callback. As a result, a downstream handler that throws by design, such as the built-in dump interceptor which throws when a response exceeds its configured maximum size, escapes as an uncaught exception that terminates the Node.js process. A malicious or compromised HTTP server can crash any client that composes the decompress interceptor with such a handler by returning a small compressed body that decompresses to more than the configured limit, so only the decompressed size matters and the bytes on the wire stay tiny. The issue is fixed in undici 7.30.1 and 8.12.2, and users should upgrade to one of those versions or later. As a workaround, avoid composing the decompress interceptor with a response handler that throws during response processing until upgrading.
Weakness: CWE-248
Which versions are affected by CVE-2026-87029?
4 open source packages ship an affected version, including undici. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
undici npm | From 7.15.0 | 7.30.1 |
undici npm | From 7.15.0 | 7.30.1 |
undici npm | From 8.0.0 | 8.12.2 |
undici npm | From 8.0.0 | 8.12.2 |
Products include Nodejs Undici.
How do I fix CVE-2026-87029?
Upgrade undici to a fixed version for your release line: 7.30.1 or 8.12.2.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-87029 being exploited?
There is no known exploitation of CVE-2026-87029 in the wild and no public exploit code.
Other vulnerabilities in Nodejs Undici
- CVE-2026-109855 undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake
- CVE-2026-109869 undici vulnerable to Denial of Service via unhandled error on excessive content-encodings
- CVE-2026-87018 undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation
- CVE-2026-19534 undici vulnerable to Denial of Service via unrequested WebSocket subprotocol
- CVE-2026-12151 undici WebSocket client vulnerable to denial of service via fragment count bypass
Sources
Also known as DEBIAN-CVE-2026-87029, ECHO-341d-0f3a-c605, GHSA-55wc-3pg8-jfw6, UBUNTU-CVE-2026-87029.