All vulnerabilities
CVE-2026-84947GHSA-2gqq-gqf2-x968

undici vulnerable to response truncation via oversized chunked responses in the dump interceptor

undici undicinpmLibraries & packages
CVSS
3.7Low
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.20%Chance of exploitation activity in the next 30 days, higher than 8% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed in7.29.1Also 8.10.2GitHub
Published4 Sep 2026Updated 29 Sep 2026CVE List

What fixes it

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Description

Impact

undici's interceptors.dump() reads and discards response bodies up to a configurable maxSize. When a response declares a Content-Length that exceeds maxSize, the request is aborted cleanly. When a response is sent chunked (no Content-Length) and its body exceeds maxSize, it is not aborted: the interceptor ends the response early once the accumulated size reaches maxSize, and continued delivery from the parser triggers an internal assertion that is caught and turned into a request abort and connection tear-down. The application observes a misleading 200 with an empty or truncated body while the connection is disconnected. Any application using the dump interceptor against untrusted or misbehaving upstreams is affected.

Patches

Upgrade to 7.29.1 or 8.10.2. The dump interceptor now enforces maxSize on both the declared and the received body size, aborting the request with a RequestAbortedError instead of returning a truncated response.

Workarounds

None. Avoid using interceptors.dump() with untrusted upstreams until upgraded.

Text from GitHub Advisory Database

Affected versions 8

  • undici, npm>= 7.1.0, < 7.29.1GitHub
  • undici, npm>= 8.0.0, < 8.10.2GitHub
  • undiciaffected: 7.1.0 before 7.29.1CVE List
  • undiciunaffected: 7.29.1CVE List
  • undiciaffected: 8.0.0 before 8.10.2CVE List
  • undiciunaffected: 8.10.2CVE List
  • undici, npmfrom 7.1.0, fixed in 7.29.1OSV
  • undici, npmfrom 8.0.0, fixed in 8.10.2OSV

References 8