Skip to content
EXYS
Back to the CVEs

CVE-2026-84961

9.1, critical

undici's BalancedPool constructor passes its entire options object through an internal deep-clone that serializes and reparses the value…

NVD (opens in a new tab) CVE.org (opens in a new tab)
CVSS
9.1, critical critical CVSS v3.1
EPSS, next 30 days
0.1% higher than 3.4% of scored CVEs
Exploitation
No public evidence
Published
4 Sept 2026a month ago

Description

undici's BalancedPool constructor passes its entire options object through an internal deep-clone that serializes and reparses the value as JSON. Because JSON cannot represent functions, any function-valued TLS option, such as a caller-supplied checkServerIdentity callback or a custom connector inside the connect option, is silently discarded before it reaches the TLS layer. As a result a peer whose certificate the application's custom checkServerIdentity was written to reject, but which still passes Node's default hostname and chain checks, is accepted when reached through BalancedPool. The Client, Pool, and Agent dispatchers are not affected because they extract the connect and tls options before cloning. This affects undici versions from 7.24.1 up to 7.29.1 and from 8.0.0 up to 8.10.2, and only when the application supplies a function-valued connect or tls option to BalancedPool. Users should upgrade to undici 7.29.1 or 8.10.2.

Details

Vendor
Undici
Product
undici
Weakness
CWE-295 (opens in a new tab)
Status
Analyzed
Updated
15 Sept 2026
Assigner
ce714d77-add3-4f53-aff5-83d477b104bb

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References 2

Advisories 2

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other Undici CVEs

Every Undici CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2026-84933 undici Exposure of Sensitive Information Vulnerability EPSS 0.3% 8.2, high
  • CVE-2026-85014 undici's experimental WebSocketStream client crashes the whole Node.js process when a remote peer closes the TCP connection without a… EPSS 0.4% 7.5, high

Beyond this page

Is CVE-2026-84961 in your network?

This page tells you how dangerous CVE-2026-84961 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

  • EXYS7600 OCELOT

    Find it before attackers do

    Ocelot scans your network on a schedule and reports every vulnerability it finds by its CVE identifier, with its CVSS score and how many of your hosts are affected. A finding like CVE-2026-84961 comes with the devices to patch.

    Learn more about EXYS7600 OCELOT

  • EXYS7950 KONDRA

    Detect it if it's exploited

    Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.

    Learn more about EXYS7950 KONDRA
Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 17 Oct 2026, not the live upstream state.