CVE-2026-109383 undici - Authentication Bypass

undici 4.0.0 to 6.29.0, 7.0.0 to 7.30.0, and 8.0.0 to 8.12.1 contain a broken authentication caused by JSON-based deep cloning dropping custom checkServerIdentity callbacks in TLS options, letting attackers bypass custom TLS certificate verification, exploit requires passing a function-valued tls option.

CVSS base score 7.4 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
View the NVD record ↗

Details

Type
Broken Authentication
Impact
Man In The Middle
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Published
15 October 2026
Updated
16 October 2026
Weakness
CWE-295

Vendor fix

Upgrade to undici 6.29.1, 7.30.1, 8.12.2 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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