undici: Improper Certificate Validation
CVE-2026-109383 is a critical-severity improper certificate validation vulnerability in undici, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 6.29.1, 7.30.1, 8.12.2 as the first without the flaw, so updating undici to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.18% chance of exploitation within 30 days, which is low compared with other CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update undici to 6.29.1 or 7.30.1 or 8.12.2, whichever matches your release line, or a later version.
- Read the advisory on cna.openjsf.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Undici | undici | 4.0.0 up to, but not including, 6.29.1; 7.0.0 up to, but not including, 7.30.1; 8.0.0 up to, but not including, 8.12.2 | 6.29.1, 7.30.1, 8.12.2 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.4 | High | CNA |
| CVSS 3.1 | 9.1 | Critical | NVD |
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Certificate Validation
The product does not validate, or incorrectly validates, a certificate.
How developers prevent this class of flaw
- Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
- If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.
More Improper Certificate Validation vulnerabilities (CWE-295)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in undici
- 7.4 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
Recent Improper Certificate Validation vulnerabilities
- 8.0 High severity
- 9.1 Critical severity
- 9.0 Critical severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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