Improper Certificate Validation Affecting undici package, versions >=4.0.0 <6.29.1>=7.0.0 <7.30.1>=8.0.0 <8.12.2
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-JS-UNDICI-21181005
- published18 Oct 2026
- disclosed15 Oct 2026
- creditEurico Nicacio, Sanjeev Kumar, BlueN0r
Introduced: 15 Oct 2026
NewCVE-2026-109383 (opens in a new tab)How to fix?
Upgrade undici to version 6.29.1, 7.30.1, 8.12.2 or higher.
Overview
undici is an An HTTP/1.1 client, written from scratch for Node.js
Affected versions of this package are vulnerable to Improper Certificate Validation via the Agent constructor in lib/dispatcher/agent.js, where TLS options passed as the tls parameter are silently dropped and never stored in kOptions. Because the tls field is not destructured and forwarded to the internal options object, any TLS configuration supplied by the caller - including custom CA certificates, certificate pinning, or hostname verification overrides - is ignored when connections are established. An attacker positioned on the network can exploit the resulting absence of TLS constraints to perform a MitM attack, intercepting or modifying HTTPS traffic that the caller believed was protected by the supplied TLS settings.
Workaround
Users who are not able to upgrade to the fixed version are advised to pass the TLS options through connect instead of tls. For proxied EnvHttpProxyAgent destinations, use requestTls / proxyTls.