undici vulnerable to TLS certificate validation bypass via dropped connect options in BalancedPool — GHSA-W293-VG96-WGC3

Summary

### Impact undici's `BalancedPool` passes its constructor options through a JSON-based deep clone (`JSON.parse(JSON.stringify(...))`) before forwarding them to each per-upstream `Pool`. JSON cannot represent functions, so a caller-supplied `connect` or `tls` option containing a `checkServerIdentity` callback (or a custom connector function) is silently dropped before it reaches the TLS layer. As a result, a TLS…

Timeline

Published by source

2026-09-29

Risk context

• Reported severity or threat level: high.
• Reported CVSS score: 7.4 out of 10.
• Reported EPSS value: 0.00248.
• Review exposure for the affected product or family: npm: undici.

Product

npm: undici

What to do

General, cautious steps (verify details in the official source):

• Prioritize patching or mitigation immediately (treat as actively risky).
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-W293-VG96-WGC3

Source

GitHub

Vendor

GitHub

Published by source

2026-09-29

Last source activity

2026-09-29

Additional identifiers

CVE-2026-84961

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.