CVE-2026-109383

9.1

undici is an HTTP client library for Node.js

CVSS: 9.1, critical critical CVSS v3.1
EPSS, next 30 days: 0.2% higher than 7% of scored CVEs
Exploitation: No public evidence
Published: 15 Oct 20265 days ago

Description

undici is an HTTP client library for Node.js. In versions 4.0.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its Agent dispatcher passes its constructor options through a JSON-based deep clone before forwarding them to each per-origin pool, and because JSON cannot represent functions, a caller-supplied tls option containing a checkServerIdentity callback is silently dropped before it reaches the TLS layer. As a result, a TLS peer whose certificate a custom checkServerIdentity was written to reject, but which passes Node's default hostname and chain checks, is silently accepted. Because Agent is the default dispatcher behind request, fetch, and setGlobalDispatcher, this affects the path most applications use, and EnvHttpProxyAgent is affected on its direct and no-proxy routes as well, while only applications that pass a function-valued tls option such as a custom checkServerIdentity for certificate or public-key pinning are at risk. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, which preserve the tls option outside the JSON clone so custom verification callbacks are forwarded unchanged, and users should upgrade to one of those versions or later. As a workaround, pass the TLS options through connect instead of tls, or for proxied destinations use requestTls and proxyTls.

Details

Vendor: Undici
Product: undici
Weakness: CWE-295 (opens in a new tab)
Status: Analyzed
Updated: 19 Oct 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-2026-109829 undici is an HTTP client library for Node.js EPSS 0.1% 9.1, critical
CVE-2026-109841 undici is an HTTP client library for Node.js EPSS 0.3% 7.5, high
CVE-2026-109924 undici Allocation of Resources Without Limits or Throttling Vulnerability EPSS 0.3% 7.5, high
CVE-2026-109932 undici Uncontrolled Resource Consumption Vulnerability EPSS 0.3% 7.5, high
CVE-2026-87029 undici is an HTTP client library for Node.js EPSS 0.3% 7.5, high
CVE-2026-84961 undici's BalancedPool constructor passes its entire options object through an internal deep-clone that serializes and reparses the value… EPSS 0.1% 9.1, critical
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

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Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 20 Oct 2026, not the live upstream state.