GHSA-4qv8-2p9j-2685

ghsaUSosv

undici vulnerable to Denial of Service via unbounded memory in the EventSource parser

view advisory published 2026-10-23Licence: CC-BY-4.0

### Impact undici's `EventSource` client can be driven to exhaust process memory by a malicious or compromised Server-Sent Events peer. By sending millions of tiny completed `data:` fields with no blank event separator, or a single unfinished line split across many chunks, the parser retains a growing amount of per-field and per-chunk state. The byte-based `maxEventSize` and `maxResponseSize` limits do not bound that retained state, and `maxResponseSize` is enforced on the compressed body before decompression, so a small compressed response can expand into enough retained memory to terminate the process. The application only needs to maintain an `EventSource` connection to an untrusted peer, which controls only the response. Availability is the only impact. ### Patches Upgrade to `6.29.1`, `7.30.1`, or `8.12.2`, which bound the retained EventSource parser state (the number of `data` fields and buffered chunks, the unfinished-line length, and per-field byte totals) independently of the byte limits. ### Workarounds None.

01

describes (1)

Related CVEs.

IDseverity exploitable
CVE-2026-109924UShigh7.5—
undici is an HTTP client library for Node.js. In versions 6.5.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its EventSource client can be driven to exhaust proc…
02

references

External citations — patches, advisories, analysis.

scry

Advisories like this name the exposed products attackers go after on your perimeter. See what is exposed on your perimeter with a free passive scan.

Free scan